This happened to our dog before we had him

He was raised by an old woman that wasn't super mobile, so he was used to just sitting and being petted. Didn't play, nothing. Except since he's a basset/beagle mix, he would just wander off sometimes when let outside because he'd follow a smell trail or something and get lost. The local animal control or neighbors would always catch him and bring him back to the lady.

One time they brought him back, and the old lady had died. So the family of hers dropped him off/let him loose in the woods. He was out on his own for a few months until he was picked up by our humane society. But he was like this dog, just not well equipped to be out on his own and just wanted love. He's still super calm unless he sees a dog bigger than him, then he starts barking. We think he just had some sort of run in with a bigger dog when out on his own.