All you can do is back out and build up your Exhibitionism Skill. You'll need at least lvl 3 I think. It might be lvl 4 whenever you can openly walk around your dorm naked. Is when you can do it at the party.
My exhibitionism is at 5 already. That's why i think there must be a bug. I've been walking around the party nude with no problem, it's once I've had the encounter upstairs that I can't go anywhere.
