Idea
You right hand fan the deck to reveal it is blank. You take the spectators card and leave it out-jogged in the fan. Close the fan and move it to left hand grip. Now when you fan the cards, the deck has returned to normal and the selection has turned blank.
How can you change the card that is sticking out?
(all ideas developed by the community will be released at one point as a free release from the community)
I will need to experiment and get back to you then...