I've come across this a few times over my career, and I had another one yesterday: variations of a very mean note about a student being found in a very classroom-public place... and no way of determining who did it. If you have had this happen before, how do you handle it? Since it happened at the end of the day yesterday, I assigned each student the name of another student to write five nice things about them, as a ticket to recess. In retrospect, it felt forced and unnatural. But I also hate to take away recess or other big things like that.