Is this perhaps one of those situations in which someone purchases items on a card, then figures out a way to return them for cash in order to make it appear as though the card purchases remained intact? If so that explains why it might take a while to discover and also why someone may be upset about this (though I imagine that someone would be Citi/the retailer; AA got paid by Citi for those miles and shouldn't care). That's assuming we're taking the OP at face value and s/he didn't realize the importance of such details.