Rumpole
Formerly known as "Hercule Poirot"
If you find one EXACTLY matching one the LE have found but have not shown us, and the sheet has at least one sticker missing, I bet your prints are on the backing sheet.I went for a rummage around my house and found 3 different types of stickers and an adhesive sheet of reflective design similar to the sticker sheet found in KC's bedroom.
Every single one of them is foil, not paper on the adhesive side, which suprised me.
Here are some pics. I have put the finest (lower right pic , 3rd sticker) in a bowl of water sitting in the sun (currently 107 F) to see how long it takes to break down, if at all. I think this one will, but it might take a while.
That makes YOU guilty!