Math class incident?

Last week was my first week back at school. Algebra is my first block, and we were going over material that would be on a quiz. I was Schreiben down some stuff, copying answers, and this guy I've been talking to for about a week turned around, put a dime on my desk, gave me a thumbs up, then turned back around. Does this mean anything, oder was he just being weird? I kept the dime, and I plan on asking him tomorrow what he was doing.