Gamestop has a bad habit of selling your stuff even if you reserved and actually put money on it.
They've done that to me a couple of times. One was when I had reserved Metal Slug Anthology for the PS2 only for it to be pushed back something like 4 months. I didn't even know they had finalized the date as Gamestop didn't call me or anything.
I found out on a gaming site that it had finally come out and when I went to get my "reserved" copy they had sold it to someone else. Morons.................