I play rugby, but I wear a scrum cap. On one occasion I have had the cap grabbed very violently in a way which caused the piece underneath to be ripped and a few hairs to fall out. Nobody saw anything suspicious though - so no detection implications, and I was able to repair the tear afterwards.

Just common sense really. You are wearing a piece of fine netting stuck to your head with hairs tied to it. If someone grabs and pulls your hair it could tear the mesh or pull some hairs out. You have to protect against that. Unlikely that they could pull your whole piece off though.