If someone had found my purse and handed it in, intact, I know I definitely would want to show my appreciation. If it was a total stranger who had left details with the police, then it would probably be a Thank you letter, as this is someone in the same village and the shopkeeper knows them, I would leave a note and a treat, as the others say, a nice cake, even a good shop bought fruit cake or something.If he didn't like it, he could give it away to someone he dog walks for.You are never going to hit on the perfect thing, as he could be diabetic, may not drink for health or religious reasons, you could just torment yourself that way. I think he would be really happy to receive a cake via the shop keeper as he obviously doesn't want a fuss or you to meet him etc, it just shows you have thought about him and are grateful.