Maybe his owners dumped him off, it happens. The guy who found him just might have himself a new buddy.
Please no one ever assume that ^^^ if a pet is found, until all avenues have been exhausted. Some family could be heartbroken out there looking for him. Too many have taken animals into their own homes just assuming they're abandoned when not.

I know somebody who did this on military installation

found the "abandoned" dog and brought it home

I only heard the story in about 5 years of retrospect so not much I could say at that point.
I hope the dog wasn't abandoned and is returned to a happy home.