I've been caught a couple of times.
I was driving interstate and I had a disposable diaper on which was ready to burst. I'd put a pair of plastic pants over the top at the last stop, but even these couldn't contain the leaks. I pulled into a service station to refuel and while I stood there at the pump, my diaper bulge and tell-tale wet spots was pretty obvious. But it was the plastic pants and the back of the diaper sticking way above my cargo shorts that got the attention of the people in the car beside me. Then I noticed that the weight of my diaper was causing my shorts to slide down off my hips but with both hands occupied with the fuel pump, I couldn't stop them from dropping past mid-thigh and thus revealing my entire diaper and plastic pants to the cars around me.
Another time was also on an interstate drive when a guy in the cubicle beside me decided to look through a peep hole, hoping for some action. But what he saw was me putting a fresh diaper on while standing against the wall of the cubicle. I was in the process of taping up the diaper when I saw his eye staring at me. I took my time and gave him a show as I pulled on a pair of plastic pants, a pair of briefs and then my shorts.
I'm sure there's been other times when people would have seen the back of my diaper poking out of my pants when I bent down.