Sorry to hear about your cat. Try not to worry , he will probably find his way home...not to where he was cared for but to his 'normal' home. Meanwhile, phone the local vets. They usually have a 'lost animals' book where they will record your (and his) details so that they can be aware of someone comes in with what they think is a stray. Contact your local Cats Protection League or any other local cat shelters as they will keep an eye out for him if he is brought in as a stray. It can be worth putting a few posters up round about so that your neighbours etc are aware that he has gone missing. (Depends just how rural the area you live in is, I guess. ) In town it would be worth asking the postie to keep a lookout for him, but maybe not so appropriate in the country.
I hope he turns up soon.
Let us know if he does.