Vet Called And Said Neighbors Stole Our Cat

Location: Florida

Our vet called and said that the neighbors down the street came in with out cat, whom they recognized and verified the chip of.

The neighbors claimed he used to have a collar but now doesn't and is obviously abandoned and abused and always coming "starving" and begging for food. (He is overweight).

They ordered expensive blood work. Note that this is the best and most expensive vet in our area.

They have since left the vet office. We were given their name and phone number, but they are not responding.

It's been about an hour now.

Does it make sense the vet sent the cat home with a stranger after confirming our ownership?

I plan to go knock on their door in a few moments, but am worried they will say they don't have him.

What paths forward do we have?

I'm afraid of causing contention with a close neighbor, but they can't just steal our cat.

We will do our best to keep him inside from now on; he escapes out the back door and goes and visits the neighbors and most of them know he lives with us at this point. I find it hard to believe this neighbor didn't know.

He is a pretty siamese cat and I think they just wanted to keep him, as one time he came home with a collar which we promptly changed and put our number on (only for it to mysteriously disappear).

Update: This was a lesson in not freaking out. The neighbors came home and I ran to their house and they were really nice and apologetic. I feel bad now for freaking out, but my sister had her siamese actually stolen once by a neighbor (different city) and when confronted they got rid of him under mysterious circumstances and he was never seen again. I thought this was that all over again.

Other than saying he was starving (though I can now understand based on how he acts).

Planning to be more vigilant about keeping him inside. Learned he has more than 1 family he visits.

Thank you all. There are good people.