So, this is what happened. I was taking a shower. My washcloth was laying across the top of the shower doors. I was washing my hair. I know I did not hit the shower door, as both doors would have rattled. There was no rattling of the shower doors. The washcloth came off the top of the shower door and hit me on the side of my face.
I spent quite awhile trying to recreate the washcloth falling off the shower door. I used the same wet cloth and a clean dry cloth. I was unable to get the cloths to fall. I opened and closed the doors. I rattled the doors. I banged the doors. The cloths stayed right there on top of the door.