What I'm asking (without spilling the beans) is whether that card can be returned to normal condition, for example by rubbing it magically in just the right spot.
First of all, they're so astounded that they really don't give a crap what you do next. Toss them on the table, put 'em in the deck, whatever. What I do is toss 'em down, pick up the deck, replace the cards in different locations (with 2 at the top), turn the deck face up, and clean up from there. Easy enough.
yeah...i perform that trick a ton because it gets great reactions and is relativley easy. Once you finish the final revelation just grab the cards and casually put them in the deck, i havent have anyone who has wanted to inspect the cards. If they do you could just hand them their card or just move on to another trick.
So that card is forever 'special'? I'm not so worried about the immediate aftermath of the trick. I'm more concerned whether that card might gum up the next trick I perform. Sorry to be so vague. I'm trying to protect the secret of the trick.
I don't think you guys are quite understanding the question.
If my interpretation is correct and you're concerned about the everlasting dirtiness of the card, then I just suggest you keep that 5 for that trick. I had the same problem and it was frustrating, so I just kept it as my "5 Speed card."