Strap, sew, buckle, put a chain around connected to your belt loop, or put it in your socks. I'm paranoid to lose or get my wallet stolen. Secure that, soldier!
It seems he got a little overzealous or had too much to drink, but there’s no excuse for such behavior—it’s sexual harassment and assault. Actions like that are not just irresponsible; they’re outright unacceptable. He should take a moment to reflect: if he had a daughter, would he want her to be treated that way?