I like NyaChan's wording best so far. The points I, personally, would want to convey are:
--thanks for all the stuff you did
--the wine was wrapped up and thus in my mind "set aside"
--the wrapped wine was expensive/we were saving it for a special occasion
--partly also my fault for not communicating more clearly
--the wine is your thank you gift... Maybe, "Under the circumstances, please consider the wine our gift to you as thanks for your help"?
Made one little change to make sure that the point gets across that the wine that they drank (three bottles in ten days, especially that ONE bottle) was not quite what they had in mind when the words "make yourself at home" were said.
I don't mind house sitters using my bath soap, shampoo, towels, bed (as long as they wash the sheets), dishes, and a reasonable amount of food. They can read the books on the shelf, watch the movies on the shelf by the entertainment center, and the like. But stay out of my underwear drawer (even if you wash it), my makeup, jewelry, and any "really personal" stuff (come to think of it - at least some of that stuff is also stored in the underwear drawer - I used to keep my diary there, as a teenager - burned the diary and all potentially embarrassing correspondence also saved in that drawer before getting married).
I'd suggest a lock & key on the bottom doors of the wine cabinet, if the OP and her husband plan to have people stay with the cats again - then leave any "not to be shared" items locked up - to deter any guys from looking further - leave a box of tampons on top....
In fact, if ONLY guys are doing the cat sitting, cutting out some boxes and setting up a stack of tampon boxes in such a way that the bottle is nestled in tampons would probably keep a bottle of wine safe from most men. Now, if he has a GF over and she needs a tampon, the hidden wine might be found...so it might not be completely, 100% guaranteed to keep anyone from finding that bottle...but it would slow them way, way down....