Yeah I experienced that before. For measure of precaution, I take the cleaning magnet out when there is lots of people over and can not keep an eye on what may happened.This weekend, my wife had friends over. One of her friends just walked down stairs and looked at my tank. No problems there. But then she started taking my flipper scraper and started to clean my glass. I had to gently take it away from her with a smile. it was uncomfortable for me. We talked for a while and keep asking why my nemo can't have a Dory in there lol fun disussion. She is curious which is fine, but very touchy touchy.
Like vetteguy was saying, I need to set the rules.