Apparently, that ragamuffin who works in the library didn't seem to appreciate it when I tried to put a stop to her--well, she was talking to my brother, which was simply inappropriate. She apparently took offense at telling Ron to keep a proper distance, and took her revenge with a bucket of mud in my bed.

I know it's her, because a proper wizard would never have used a bucket of mud! I am simply irate that her grubby little wandless hands would resort to something as insulting as putting mud in my bed.