O.k. Go to this site and do what it says (It dosen’t take long, promise.) If you know exactly how this works please tell me cuz I am baffled. Thanks 
http://www.btinternet.com/~appleby.manor/andy/ajsdocs/ajsprank/carda.htm
Easy. All the cards in the second viewing are different from those in the first.
Look closely. All the cards are changed.
Simple. NONE of the cards in the second set are present in the first set. In other words, it starts out with 6 cards being displayed, then displays 5 completely new cards. So, of course, the card you chose disappears.
Oh, jeez. Duh. Now I see. You do realize that I feel like a moron now for not realizing this sooner. Thanks anyways
If it makes you feel any better, it’s specifically designed to be difficult to figure out–otherwise, it wouldn’t be much a trick. First off, the very premise of the trick is to get you to concentrate on only one of the cards, so that your mind is only tangentially aware of the other cards, anyway. Further, the replacement cards on the next page are similar enough in suit and value distribution so as not to be obvious that none of them have the same suit AND value as the originals. All you really notice is that YOUR card is no longer there.