Oh, no... Was it possibly his dog that was seen, but could not be located when he got there? ..or just not his dog?
Hope he turns up soon... Would be sure the missing dog information is kept up, out there, contact whoever had him as missing and let them know the owner is still looking and please keep him as a missing dog.
Been there, done that with a cat years ago....and he did turn up because the finder called her vet to say there was a kitty on her deck ..appeared to be on it's last leg..and that vet still had my flyer on their bulletin board ..description matched..gave finder my phone number...we went up to her house and there he was She had brought him in and given him food. Always appreciated that so much...
I had called local vet's etc..asking if they would leave his info up..and they did. Big payoff!
So, don't give up yet!