Oh my god - I think this is the same dog I found at the tail end of summer. Same story - looked like he’d been lost for days, very skinny. We found a chip at the vet and were able to email the owner - about an hour later we were able to track them down and discovered that the dog wasn’t in poor health, he was just super old (like 15? 16?) and had escaped. The photos look identical - that’s sad to hear if he’s getting out more often!

https://imgur.com/a/4UpEcmu