I'm out for dinner, drinking a couple of beers with a friend. I excuse myself to use the restroom, do what I need to do, wash my hands, and approach the paper towel dispenser to dry them.
Crap! It's one of those motion-detector dispensers.
I wave my hand in front of it. Nothing.
I move closer and wave again. Nothing.
I wave harder. I back up and wave. I move my hand toward, then away from, the little red light. Just as I start doing my silly little "what-a-stupid-situation" dance in front of it (cue the sarcasm), someone walks into the restroom. She's a bit startled, so I explain: "The paper towel dispenser doesn't see me."
The woman kindly waves her hand in front of the dispenser, which obediently provides her with a paper towel, and locks herself into a stall. I dry my hands and re-join my friend.
I'm invisible to paper towel dispensers. Consistently. No matter what moves I make in front of them, no matter how hard I concentrate to be corporeal, I simply don't exist to them. Motion-detector sinks? No problem. Soap dispensers? They squirt me every time. But I'll be damned if I can dry my hands without using the legs of my jeans. There's just something about paper towel dispensers.
Well, ok, and the occasional automatic door.