Other videos are showing it was a piece of paper (card sized)
What about a handkerchief? I don't know why he'd put that on the lectern - and it wouldn't have been okay, in any case - but I'm just playing devil's advocate and trying to think of other things it could have been. (In the Globe video, it sure looked like a piece of paper to me, too.)
You can tell he tried to pull it out while his back was to audience .I dont think he knew a camera was back there.
I watched several of the videos and checked out the still frames. I couldn't tell. Need someone to blow it up and clean it up to be sure.