I do this on a daily basis...
I'm at the drafting board, drawing, and I get up to answer the phone or check e-mail or whatever, and I take my pencil with me. I end up putting it down somewhere else in the room without realizing it. Then I go back to the drawing board and grab another pencil out of the tray next to me. Then I get up again... and repeat. And repeat. Eventually all my tech pencils are spread throughout the room (and occaisionally in other rooms) and I finally have to go on a "pencil hunt" with a backpack full of dry rations, a pith helmet and a pencil-sniffing bloodhound.
I suspect I'm not the only person to do this. ::hopes::