kept as a pet because when he (allegedly) tried to release the squirrel it turned up at his door sometime later injured again

My friend's dad cut a tree down in their yard that had a squirrel nest in it. He didn't know about the nest when he cut the tree down. Unfortunately the mom died when the tree was felled, and the babies couldn't survive on their own. My friend's family bottle fed the babies and raised them until they were old enough to be released. The squirrels never left. They'd run around in the trees and stuff, but they'd come back to the house, wanting to go to tier little beds at night, and get free nuts and stuff. They'd also tear around the house if the weather wasn't good that day. So, I completely believe that the squirrel came back after being released.

Edit: before the NYC animal department gets any bright ideas, this was 20 years ago, and in a completely different State.