I once had to change in a stall that had a big hole in the partition (aside the tp holder). I didn't realize it was there until I had removed my old diaper and was starting to put on my new one. Sure enough some weirdo was peeing through that hole. I just said enjoying the show, and finished up. I washed my hands and left before he came out or anything was said.
I also had another time I was in a locker room, and had changed out of a swim diaper and dried off. Right as I pulled the new diaper up between my legs, some 10-12 year old kid walked in. lol, we both froze for a second, then I just continued to just diaper up and get dresses. Again, nothing was said.