I'm guessing you have some laundry to do. Be careful washing it and follow the instructions carefully.
The British way is to pretend like nothing happened, but you could try convincing your room-mate that his bride-to-be takes huge quantities of LSD maybe and hallucinated the whole thing, but that's probably a non-starter. You could tell them you woke up in the bathroom after having the strangest dream.
Nope, don't think that would cut the mustard so maybe you might be able to use the mustard elsewhere because you're going to be eating a particuarly unsavoury type of sandwich.....