Only once . I beat a hasty retreat. No harm done.
But the most comical instance I ever saw was one lunchtime in the Sydney Domain. The men's toilets are separated from the men's showers by a tiled walkway about three metres wide. It's well signposted but is wide enough to look like a path.
I went for my usual run one lunchtime and was in the shower/change room with about 25 joggers and footballers, all in various states of undress, when a woman walked past the space that served for a door. And glanced to her left.
What was funny is that she didn't seem to believe what she had seen and after she'd passed the doorway, her head popped back around while she had another look.