I'm sure you've already done this, but if the dog didn't have a collar, did you take him by the vet to make sure he wasn't microchipped?
Lots of people who spend a lot of money on pure-bred dogs (even lots of people with mixed breeds) spend the $10 to get their dogs microchipped in the event that they get lost and lose their collar.
I only ask, because someone is probably missing their doggie right now
My dog's trainer once told me a story of one of her friends who adopted a stray dog and took it to a dog festival where a clinic there was doing free microchipping. Before they inserted the chip, they obviously scanned the dog to ensure it wasn't already chipped. Well, this dog turned out to already have a chip and they had the dog for over 2+ years. They ended up finding the original owners and giving the dog back.
It's a sad story
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