Jon stepped into the locker room, then decided to take a shower. Yes, he just wanted to get out of there, but he was really sweating a lot and it was a good idea to just wash off all the perspiration. Too bad he couldn't wash himself of the entire experience as well.
So, after taking off his gym clothes, he headed to the shower area and cleaned himself off. But after he turned the water off, he suddenly felt this odd feeling wash over himself. He was planning to head back to his gym locker and put his clothes back on, but instead, he grabbed a towel, wrapped it around himself, then left the locker room. He had this weird feeling that what he needed to wear was actually somewhere else.
All of this happened in accordance to Mikey's "musical closets" wish, where he stated that "whenever Jon gets undressed and takes a bath or shower, he goes into someone else's room and puts on the clothes there instead". Jon had just taken off his gym clothes and taken a shower, so now he was headed to a different room to take someone else's clothes as his own.
But what other room was Jon heading to?