yeah, mine was up on my account for about 3 days.
my guess is this: a hold is placed on your account for about 3 days and the bank or whatever verifies the charge and if it isn't verified or if the transaction from the supplier doesn't go through, then it drops.
in this case, apple only charges your card/account when it ships..and since i ordered mine june 8th, it obviously wasn't going to ship out june 11th so that's probably why the charge got dropped. now i'm just wondering when they're going to actually charge it again.
i'll give them a call this afternoon when i get back from lunch..