The gun was found in the leaves at 59th and Lancaster on Saturday morning.
Police say the scene is just a few yards away from where 17-year-old Overbrook High School student Bernard Scott was shot and killed a few days ago.
Investigators say Thursday after school Bernard and 60 other teenagers were here when a fight broke out and shots were fired.
Bernard was hit and later died from his injuries at an area hospital. A second teenager was also wounded in the gunfire and continues to recover.
Police sources say it appears leftover shell casings do not match the revolver that was discovered Saturday.
Police also say that several teenagers had weapons and it's possible the gun belonged to one of them.
Officers found two guns at the scene Thursday and tracked down another in an alley on the 1600 block of 60th Street near a suspect's home. Four guns have now been recovered.
"This isn't working for anybody. Now we have dead boy. We have one boy going to prison. Where's that getting anybody," said one resident.
Investigators are trying to figure out if a student stashed the gun before going into school yesterday or if it was thrown here Saturday morning?
The question also remains did officers miss it during their initial search Thursday?
In scene video shot Thursday, officers were standing just feet away from where the gun was found.
A father, who did not want to be identified, was concerned about bringing his children to the playground but defended police.
"It's possible. It's human error. I mean you have to give the cops a break, they didn't put the gun there," he said.
Police sources say the gun recovered Saturday will be checked for DNA and fingerprints.
An investigation into the shooting continues.