You shrug your shoulders, thank them for their honesty, walk back to reception and either get your money back or see who else is available. It's not a massive deal. Could be any number of reasons and if it's nothing to do with personal hygiene you don't take it personally.

Not the same thing, but I've also never understood why guys get so shitty if a girl turns them away in a bar for example, just shrug your shoulders and get on with your life, getting all agro and confrontational about it only further proves the girl was 100% correct in her original decision.