Her towel got caught inside, and was pulled right off of her as she climbed out.

(chapter originally by Misayaka on writing.com)

Chihiro felt very light as she climbed out of the waste bin.It didn't take long for her to realize why. She was halfway out of the bin, leg extending to the ground, when with a barely-withheld shriek, she realized she was topless, and the rest of her wasn't exactly well hidden.

Her towel had to be stuck inside!

The halls had just emptied. There was time to retrieve it! A quick look around, and Chihiro hesitantly climbed out, rummaging through the bin for her lost towel. She'd be fine once she found it.... or so she thought, if not for one major obstacle...