While coming home on a X-country yesterday I caught something out of the corner of my eye, like something fell off of the co-piot seat but there was a noise associated with it. I keep a spiral bound steno pad under the flap handle that I use for writing squawk codes and frwquencies on and when I'm flying X-country I lay it in the co-pilot's seat if unoccupied. Anyway I was on flight following and being handed off so when I grabbed the pad to jot down the new freq. a well worn page separated from the spiral wire and was left on the seat aloung with a clip board containing some airport diagrams and such. I have yet to find that piece of paper, I'm certai that it must have been sucked out and that is what I heard and caught out of the corner of my eye. I thought the door sealed off all but at the top rear. I knew I could see a small gap up there but didn't know there was one at the bottom too.