Public restroom experience

So, the other day I went out to eat at Red Robin with my family. I went to the restroom and headed to the urinal to... extinguish a fire, and I hear someone struggling in the stall. I tried to ignore his strained grunts and groans, then a few seconds later I hear "grrrrrRRRRAFHHHGAAGH-- *plop*." Then he sighs and says "ahhh shit, I knew it!"

What the hell did he know?

There was a hole in a restroom, so I put my penis in it and waited for someone to take care of me.

When someone finally did, I found out it was a man in a woman's restroom!