Panicked, Jon froze. After the fact he was sure that if he had tried he would have been able to find a place to hide his naked body to save himself the humiliation, but at that moment the world seemed to stop for him.
That's why, when the girl's tennis team walked into the locker-room he was found standing in the middle of the room, buck naked, face red with embarrassment.
First they paused, staring at him, unsure what to do about it, then the first giggle started. That turned into another, and another. It didn't take long before all the girls were guffawing, pointing at him (well, rather at his penis). A couple girls were laughing so hard they were crying. Jon wanted to crawl under a rock and die.