Montag stood by him during what he called the "wildest day ever of either of our lives" and sparked hope that she might drop her divorce filing, Pratt said Monday.
"It was clear we're soulmates. I don't see any reason we can't get back on track," he said in Los Angeles after Saturday's incident.
Police in San Jose, Costa Rica, said the couple were briefly detained at the airport for illegal arms possession after security officers found two unloaded handguns in their luggage. Pratt and Montag hadn't declared the weapons and lacked permits to have them in Costa Rica, police said.
After questioning, they were released and allowed to leave the country, police said Monday.
The couple met on MTV's popular reality series "The Hills" and their April 2009 wedding was featured on the show. Montag, 23, cited irreconcilable differences in her July divorce filing, which Pratt says won't become final until early next year.
She indicated Monday she might have a change of heart.
"As far as I'm concerned the last thing in the world after everything we have just been through is to go through with this divorce," Montag said in a text message. "But we are just taking life second by second."
In a phone call, she praised Jesus for their release.
Pratt, 27, said he'd gone on a jungle retreat in Costa Rica for self-improvement and to convince Montag he could give up his fixation with fame ("Heidi gets sick of that," he said). Montag stayed at a nearby villa while he roughed it for a month, taking an occasional break from nature, Pratt said.
He brought the 9MM and 45MM handguns and ammunition with him as protection, traveling by private jet to and fromCosta Rica with the guns locked in his luggage, Pratt said.
"I wouldn't have gone on a commercial flight" with weapons, he said. "I wouldn't be that reckless."
After returning to California together, Pratt asked Montag if he could join her at a fundraising walk for cancer last weekend. She agreed, and now Pratt wants to keep the magic alive with his wife, whose forays into plastic surgery have made her a tabloid favorite.
Noting that Montag's 24th birthday is Wednesday, Pratt said he hoped to use the occasion to "sweep her off her feet."