My friend needs advice.....?

If she really likes him she should not be worried about this, but instead approach it with humor... it is funny! A sense of humor is a great attribute, if she can see humor in it then that is more for him to like. Also, approaching someone you like is tense in any situation, this could be the perfect ice breaker for her! What we are worried about when approaching someone we like is embarrasement, at least she has that out of the way. She could just walk up and ask him to help her find her clothes or if he has an extra towel just in case someone takes her clothes. Make a joke of it and let her sense of humor shine through, I am sure he has been embarrased before!