A few times I had it where my one of the balls on my PA has unscrewed and become loose and fell down my trouser leg - luckily no one was around - it always happens at work where no one knows I'm pierced. Once my whole PA slipped out too! It makes quite and noise dropping on a wooden floor lol
I lost my favorite PA piece in a Barnes and Noble that way. I only realized it when I made an adjustment upon getting in my car. I was not going to go in and look for it. I only hope the person who found it gave it a good home! XD
I've had my PA balls fall off and down my pants leg numerous times in a variety of places: Subway station, Sidewalk, Restaurant, Supermarket, Gym Lockerroom, Dinner Table, Campground, Middle of the Street, etc. I've only lost it once! In fact, I found the one at the campground a year later!
I lost a 28mm ring recently. Managed to knock it off when pulling my member or from under my swimsuit to relieve myself. :-/ It was falling to the sea bed before I realised what I'd done and the water was to rough to allow me to find it in the sand. So now I only have seven, which disturbs my sense of symmetry. :-)
I have this problem with rubber rings. My balls tent to retract when I'm soft so the cockring doesn't stay put. I guess my thickness is much more hard than soft. Still, I'd like to try getting fitted for a stainless steel cock ring so I can check out the difference.