Huh?

Question. Why is there a pair of panties (if it's one item, is it still "pair of panties"? anyway..) on the chair? One of my students got up to go down the hall. As I passed her chair, I noticed there was something there. A ball of navy blue material. "Oh, it's panties... HUH?!" I did a double take. "Yes, it IS a pair of panties!"

Now this brought up two questions (I know "only two?"), 1. Why was she carrying a pair of panties in her hand? and, 2. Why did she leave it there, where everyone could see it? I could see if she was flirting with someone and left them as some sort of signal, but.... Huh!? Doesn't she... Wha?! Why would she... Huh?! I just didn't get it. And I still don't.