I found a puppy wandering the streets today and took it to my vets office, lucky for this poor bedraggled puppy we were able to track down its current owners, but the info held on the chip was from its previous owners who rehomed the dog because he was deaf (he was a Border Collie and apparently thats the norm for dogs who are deaf if they are working farm dogs) Anyway, the poor pup was only 4 months old, but we found its rightful owner and got him home safe and sound.
Anyway, make sure if you get a rehomed dog that its microchip information is up to date!