There's something on my back...

So, I leant down to do up my boots.  Suddenly I felt a weight land on my back. I asked Simon to look at me.  He looked me in the face (he was sitting in an easy chair putting on his boots) and didn't appear to see anything out of the ordinary. "No, look at my back!" I said.  He laughed, then instead of helping me he picked up his camera. Hm.