This is one of the simplest yet most effective mindreading illusions ever devised. How does it work?
Take another look - a careful look - at the "before" and "after" card layouts, and all should become clear:
Fig. 1 -- BEFORE
Fig. 2 -- AFTER
Do you see it? The difference, aside from the fact that there's one fewer card in Figure 2, is that none of the cards in the second layout are the same as in the first.
I didn't just make your chosen card "disappear." In effect, I made all of them disappear, and replaced them with completely different ones.
Like most magic tricks, this one depends on misdirection: because our attention and memory are focused on one particular card, most of us fail to absorb any details about the
other five. Hence, when they're replaced by a different set that looks approximately the same, we accept it as exactly the same. Abracadabra!
