Another point would be that “chipping” of cats is common today. Catching the cat alive and running a scan on it would be the only sure way to determine that nobody has a claim to it.
Look at post 57, no vet should be confused between a feral cat and a pet.
Feral cats are easy to spot, and trying to approach them gives you all the clues you need, it isn’t their looks, it is their behavior and reactions that tell you that they are not tame.
Stalking a pet cat must not have been much of a challenge for this vet.