flashstick by valentin silvin

flashstick by valentin silvin 
visually a sticker appear on sign card
Imagine:

A spectator chooses a card and signs it.
A red sticker is glue on the back of the card. Then the card is lost in the deck
Once this is done, you take a card out of your pocket, but mistake, it's not the card chosen since it does not have a sticker ...
You just have to shake the card and a sticker appears and of course it's the signed card.

advantages:
-new method
-no flap or magnet
-can be done surrounded
-easy to do
- everything is examinable