I am not going to read past the first page of this thread because I am pretty sure it will be filled with the same ideas but stated in your won words.
If I ever run into this problem, which is never anymore becuase when it does happen it is never know to the spectator as a Failure.
If I havn't already hinted it, I use an out. The spectator picks a card, memorized and put backin the deck. First I always have multiple people look at the cards, and for added securities I use Jumbo indexed cards. Now when it comes to the reveal of the card, when I show it and they say is that your card. If they answer no, I act like the deck might be missing a piece, because this trick needs all the pieces, in order to work properly. I then reach for the card box and say let me check the box that this trick has come from, and then I produce the card from the box.