If you're really annoyed about it, just bring it up. Say "hey, I noticed this", explain what you saw happen, and let her know that in the future you'll try to be more careful, but if she knows it's yours, could she please put it with your stuff?

For the record, I think you're both being immature, and this isn't the best way to solve issues. Most of the time when people post on here about issues they have where they're boarding or whatever, it's really a matter of poor communication. Communicate the issue and apologize for leaving your stuff out. Plain and simple.

Spooksandbolts wrote:

How terribly sad for you that the extensive advice you've been given wasn't what you wanted and wasn't sufficient for you to figure what to do. 
Luckyduckerpart2 wrote:
Sometimes I wonder if there is an asshat of the year award you may be competing for that we don't know about.