As I mentioned above I have left Rowdy in a motel room - when I have to - we were on vacation this past summer and had a relative pass away. The funeral was in a little town and I had no choice but to leave him in the room during the funeral. My concern is that if I tell housekeeping that there is a dog in the room and to NOT come in - that is an invitation to come in and steal him. I know, I know, I'm paranoid and not very trusting, but that is the way I feel. I always the front desk people when I check in that I have a dog with me - but I am also paranoid about that too - thinking that that information is an invitation to take him when we are not there. But since many hotels have an extra fee for pets, I feel it is unethical to not tell them.
Anyway, I always leave a do not disturb sign on the door - and we've never had any problems at all - but we haven't left him very much. I like the idea of leaving a Vicious Dog sign on the bathroom door!!!
Although we usually don't confine Rowdy - I might try that next time - leaving him in the bathroom with his bed and toys and the like. Then if someone wants to come in to steal him - well, just let them try to get that Vicious Dog out of the bathroom!
Anyway, good luck!