I think so too. In fairness they can argue that you should have confirmed the address before leaving...
If the post office can confirm and show a signature from the hotel you can inform them that you intend to persue the matter and that its a clear case of theft on their part as the parcel should still be there after such a short time. They have no right to open post that is not addressed to them ( the name ) and they should have informed the postie on his next round that no one of that name worked there.
Its a hotel so there will be younger people working there so the likely story is that she signed for it without even looking at it... it ends up being opened to see what it is, and some computer buff who works there goes "oooh nice card" and has it away.