Well, the real downside to this whole story is SE pretty much reserves the right to do whatever they want to you anytime they want for any (or no) reason at all. Our rights are limited, but as long as you keep your nose clean you shouldn't worry about this one "mark" you've gotten.
If you have a knack for getting into trouble with GMs, see if you can contact a SGM to have this matter further looked into and see if it's possible to revoke this case of false conviction, if you can sell your ignorance as sincere. But in all honesty I wouldn't hold my breath on that one.