A while back, we had an informal dinner party at our house and invited several friends. We provided all the food and drink. My invitation had said, “We had a fully-stocked bar, as you know, but if there’s anything in particular you like to drink that we may not have, please bring it.
One couple brought a bottle of wine and handed it to me ceremoniously as they came in the door. Because I knew they weren’t wine drinkers (he’s much more of a rum guy, and she rarely drinks at all), I assumed it was a gift for the hosts.
Apparently not. At the end of the evening, the husband noticed that the bottle hadn’t been opened and said, “Hey, since no-one drank that, we’ll just take it home again.” I couldn’t believe my ears and thought that either he was joking or that I’d mis-heard. Nope – he was on his way out the door and said, “Where’s that wine?” I handed it to him without a word. 1101-08
The confusion here starts with the suggestion that guests “bring your own booze” (known here in the US as BYOB). It may have been their offering for the dinner party bar to be drunk by other guests and when it was not opened, they took back possession of their own booze. The fact that the husband wanted the wine back indicates he has some further use intended for it which may include drinking it.
Had you not suggested that guests BYOB and the bottle was given to you as described, then I would presume it to be a hostess gift which you are free to use for the function or save for later consumption.