"I remember everything about that day," her husband, Keith Papini, told ABC News' "20/20" in an exclusive interview.
That day began like any other for the Papini family. It was about 6:50 a.m. when Keith said he was on his way out the door to head to his job as an audio-video specialist. Sherri was checking on their 2-year-old daughter, Violet, when Keith said he met her at the door, gave her a hug and kiss, and left for work.
That was the last time he saw Sherri before she would be allegedly kidnapped and held captive for the next 22 days.
The Moment Keith Knew Something Was WrongWhen Keith returned home from work that evening, he said he was expecting to have his wife, daughter and 4-year-old son, Tyler, greet him at the door, but only found unsettling silence inside the house.
"I looked in different rooms and couldn't find anyone," he said. "So I thought, 'Maybe they're outside,' and I looked around outside ... but at the time I thought, 'Huh, I'm sure they're all together.' I had no reason to believe otherwise."
Keith said he opened up the "Find My iPhone" feature on his iPhone to search for Sherri's iPhone and see if he could find her location. It showed Sherri's phone was near their mailbox, about a mile away from the house. At first, Keith said he thought maybe she had taken the kids for a walk to get the mail.
Keith said he called his mother and asked her if she had spoken to Sherri. When she told him no, he called the kids' day care.
"The first thing I said was, 'What time did Sherri pick up the kids today?'" Keith said. "And she said, 'The kids are here.' It was like, 'Something is wrong, there is something wrong right now.'"
"I got in the car and immediately drove down the end of our mailbox, and was anticipating I would see her walking," he said.
But his wife nowhere to be seen. Frantic, Keith started driving around, scouring their area around their property. He went back to the mailbox where the "Find My iPhone" feature had first pinpointed Sherri's phone.
"It did not take me long [to find it]. It was right off the road," he said.
Next to her phone, Keith found Sherri's headphones, which he said were tangled with strands of her blond hair.
"If she would have lost her phone driving home one day and she had put it on the roof of her car one day and drove off, you know OK, I could see that happening," he said. "But her car was at home and the kids were at school. I knew something was wrong."
Keith went into full crisis mode and dialed 911. Within hours, deputies launched a search for Sherri, and over the next several days, more than 100 people volunteered to help.
"People would see me and start crying and give me hugs ... total strangers," Keith said.
Telling The Children That Their Mom Was MissingKeith said he spent many sleepless nights caring for his family and searching for his wife.
"I was just worried about her health," he said. "Are they feeding her? Is she hot? Is she cold? Just little horrible things that I would go through."
In searching for his wife, he admits there were times of immense despair.
"There was a moment where we were heading back after we did a few mile search and we look up and we start to see birds circling," Keith said. "And I went to my knees and I thought, 'Am I really hiking out here to look for my wife and I don't want to find her right now, but I do want to find her' ... that was a tough one for me that day."
As he was dealing with the agony of losing his wife, Keith said he still had to care for their two kids, and his family and friends came to the rescue to help keep them entertained and happy. But after a couple of days, Keith couldn't hide the fact that Sherri was missing from Tyler.
"I told him I had something important to tell him and he jumped on the couch and he knew something was up and said, 'Dad, you can tell me anything,'" Keith said, through tears. "For a little 4-year-old to say that I wasn't prepared for that.
"And I just said, 'Son, mommy went running and she didn't come home and we're all looking for her right now," he continued. "And we just held each other ... and I said, 'We're going to find her and we're going to get her back.'"
One day, Keith said he found Tyler standing in front of Sherri's picture.
"He was just standing there and he had his left hand on her face," he said. "He was just staring at her ... and he just, you know, tears in his eyes with his hands on her face."
At this time, Keith, his family and friends were growing increasingly frustrated with the lack of progress in his wife's missing persons case.
"I was very upset. I wanted more involvement with everybody ... I wanted every law enforcement agency out there," he said. "I wanted Marines, the Army ... I wanted everything of course. I'm going to do everything I can to find my wife."
Sherri's older sister, Sheila Koester, who is seven months pregnant, says she focused on protecting Keith, and making sure he ate and was taking care of himself.
"I think Keith and I supported each other," she said. "He made sure that I stayed in the house and wasn't traipsing through fields, going through places, because he knows I probably would have been doing that."
The Search for Sherri and SuspectsAlthough any husband would be a suspect in his wife's disappearance, Koester said she knew he had nothing to do with it. The family knew Sherri as "super mom" and Keith was a wonderful husband, she said.
"You would hope that your child or your daughter would find someone so loving, so dedicated to their spouse," she said.
To ease any doubt, Keith consented to taking an hours-long polygraph test.
"They asked me multiple questions. He said, 'These things you have to pass with a 100 percent. You can't get 99.' To me, I was like, 'No, problem. Let's hurry this up and get this over with,'" recalled Keith.
It took at least nine days before police cleared Keith of any suspicion.
"We were going through investigating hundreds of tips, looking at cell phone data," Shasta County Sheriff Tom Bosenko told "20/20."
Bosenko said they followed up on more than 400 tips, none of which led them to Sherri.
"The investigators had basically been working three weeks straight, nonstop -- pouring their heart and souls into this investigation. But so far, no viable leads," said Bosenko.
"I don't think I ever lost hope, but it was eating away at me big time," Keith said. "Did I do everything I could? Yes or no? I just wanted to make sure I checked 'yeah' on every single thing."
The Papini family started a GoFundMe account, and they raised nearly $50,000 in donations. Then, Keith took a chance with a man named Cameron Gamble, who said he represented an anonymous donor.
Gamble, who calls himself an international kidnapping ransom consultant, and the anonymous donor set up a website and offered a large cash ransom.
"One of the big things was finding a creative way to get her story out there bigger," Gamble told "20/20."
Like Keith, Gamble was convinced that Sherri had been abducted. He was also confident that Keith wasn't involved, and that Sherri didn't walk way voluntarily.
Though investigators did not support Gamble's involvement, Keith said he was willing to do anything to get Sherri home.
"For me, I was going to do everything I could to get my wife back, and if this was going to work, I was going to try it," Keith said.
On Nov. 23, the day before Thanksgiving, Gamble posted a video online informing Sherri's alleged captors that the ransom was "off the table" and calling for the public to find Sherri in exchange for a hefty reward.
"I wanted to make it so tempting that the abductor's own mother would have turned him in," Gamble said.
The Day Keith Learned His Wife Had Been Found AliveThe next day, before dawn, Keith missed a phone call on his cell phone from a number he didn't recognize.
"Immediately after that, my home phone rang," Keith said. "It was my wife screaming in the background, yelling my name, and a CHP [California High Patrol] officer that seemed somewhat confused at the moment, like, 'What is going on?'... [the officer] said, 'I need you to be calm. I need you to be calm.' ... I already know it's her. I can tell her voice."
At first, Keith said he didn't know what happening, whether his wife was hurt or not. He could only hear her screaming.
"I get the phone and, [I said], 'Oh my God, honey.' And of course she's screaming," Keith said. "It's very emotional. And, 'I love you, I love you, I love you, Oh my God, you're here. You're back. Where are you?' And then the phone gets taken away from her. Like, super quick."
Getting that phone call and hearing his wife screaming made him feel "very mixed emotion[s]," Keith said.
"I'm panicked but I'm happy because at this point this is the first time I've heard her voice," he added. "I know she's alive."
Soon after getting the call, Keith said he told the couple's two children their mother had been found. He said he told their 4-year-old son first.
"I sat him down, and I was on my knees and he was standing up," Keith said. "And I said, 'You know what, buddy? I found mom,' and he got the biggest grin.'"
He then told their 2-year-old daughter. "I wanted to do it one by one," Keith said.
After learning that his wife was found alive, Keith raced to the hospital where she was taken over two hours away. He said at first he was not allowed into the hospital, but when he was, he raced to see her.
"I just wanted to hold her. And we just had her. We just embraced each other and cried together. And I mean, I was so happy, though. I mean -- how do you explain it? You're upset and everything at what happened, but you're happy. She's here," Keith said.
Keith said Sherri's face was very badly beaten and that her long, blond hair had been chopped off to above her shoulders. Sherri also lost almost 15 percent of her body weight.
"The bruises were just intense. The bumps from, you know, being hit and kicked and whatever else. Her nose, so dark and yellow," Keith said. "It made me sick that there [are] people out there that could do something like this."
When Sheila saw her sister for the first time at the hospital, she said she was as battered as Keith described.
"It was amazing to see her but it was hard to see her in the condition that she was in," she said. "But it was just amazing to see her alive and talking and saying our names. It was the best present that I could have ever received from anyone."
Sherri hasn't spoken publicly yet about how she got to the highway where she was found or how she was freed from her captors. The story of her release comes solely from her account to police and to her husband.
According to Keith, Sherri was bound with a chain around her waist inside a vehicle with her alleged captors. Keith said his wife told him that at some point her alleged captors stopped the vehicle on a road.
"They opened the door. She doesn't know because she had a bag over her head. They cut something to free her of her restraint that was holding her into the vehicle and then pushed her out of the vehicle," Keith said.
According to Keith, Sherri said her captors then drove away.
"Sherri obviously has one free hand that still has some kind of, something like a hose clamp if you will, and then took obviously the bag off of her head," Keith said. "She, at this point, has no idea where she's at, and gets up and basically tries to find help, runs to a house that didn't have any lights on, and didn't look what she said was very inviting, looked scary, and obviously if you could imagine her state of mind at this point."
Keith continued, "There was a junkyard or some kind of yard or something like that that she tried to get into and a big dog started barking and scared her, and then she went and familiarized herself with where she was at by standing in the overpass and noticed I-5 symbols and she knew that I-5 North is where we live. Anything past our house, you're up in Mount Shasta area."
Keith said Sherri saw lights and ran to another building. When she could not get into that building, Keith said, Sherri then ran to the freeway.
Stranded in the middle of nowhere, Keith said Sherri attempted to flag passing motorists on the highway.
Alison Sutton happened to be driving down I-5 North when she saw Sherri.
"I saw a woman frantically waving what looked like a shirt up and down, trying to flag somebody down. I was started to see her. It was dark and she pretty much just came out of nowhere," Sutton told "20/20." "If I had swerved to the right at least a little bit, I would have hit her with my car. She had, like, a wide-eyed, panicked kind of look. I figured if she was willing to risk being hit by a car trying to get somebody's attention that she must really need some help."
Sutton said she pulled off the highway and called 911. Dozens of other drivers also called 911 on Sherri's behalf.
Keith said that Sherri was trying to flag people down for an extended amount of time and that several people drove past her without stopping.
"She screams so much. She said she was coughing up blood from the screaming, trying to get somebody to stop," Keith said. "Again, just another sign of how my wife is: She's saying, 'Well, maybe people aren't stopping because I have a chain. It looks like I broke out of prison.' So she tried to tuck in her chain under her clothes."
Rescue workers raced to the scene, which was 150 miles away from the Papinis' Redding home. Sherri was disoriented from 22 days in captivity and didn't know what time or what day it was, Keith said.
"She thought it was late that night, so when the paramedics finally were talking to her, they were the first people to tell her, 'Happy Thanksgiving.' It just blew her mind and then she's like, 'Oh, it's Thanksgiving night?' And they said, 'No, it's Thanksgiving morning,'" Keith said.
Where the Case Stands Today and How the Papini Family Is HealingAuthorities are still hunting for the alleged kidnappers. Based on Sherri's description of her alleged captors, Sheriff Bosenko told ABC News that authorities are searching for two Hispanic female adults armed with a gun and driving a dark SUV.
One suspect, the younger of the two, was described as having long curly hair and a thick accent, pierced ears and thin eyebrows, Bosenko said, while the other woman, the older one, was described as having straight black hair with some grays and thick eyebrows. Police artists are now working on a composite sketch.
Keith said he is focused on what is next for his family's healing.
"You would expect that I want to get these people ... and then your mind goes into a place that it shouldn't and I think most people are doing that," Keith said. "Clearly, I want justice but right now I'm just happy that my wife is back. I don't have to raise my kids without her."
Even in the midst of the gratitude he feels, Keith said he knows his wife's road to recovery won't be easy.
"When lights are off, when doors shut, when she hears certain sounds, I mean it's something that I don't know how to deal with and we'll need somebody who can help her through that from a professional standpoint," Keith said. "I'm sure I'm going to have to reach out for something for some of my feelings as well. It's not just a long road. It's something we're never going to forget."
ABC News' Jim DuBreuil, Lynn Redmond, Andrew Paparella and Astrid Rodrigues contributed to this report.