Multiple times.

For the most part, it’s like you said: someone changing clothes, or losing them via unintended consequences like jumping into a pool wrong and not realizing it.

Many years ago, my family went camping to one of our favorite spots. As usual, I set up my tent close to the creek. Every morning after that, and occasionally if I was relaxing and reading, the campers from across the creek would be visible as they used the bushes, but didn’t realize said bushes weren’t hiding anything from our direction, only from their own camp.

I was young enough that I wasn’t going to say anything because it was a bit of a rush, and I had no clue how to go about letting them know they were entirely exposed as they did their business.