why is it that when i try to redeem my cait skin it says that the code isnt valid, i bought the magazine fair and square

Also what happens if you don't have Cait? Do you get her plus her skin?

I was gonna buy this when i was at the store. But the november issue they had, had Batman Arkham City on the cover. I was all confused.

I looked everywhere for this magazine to finally find one. Got home with much excitement only to find the code had already been used. Really really sucked