Great you caught it. I think it is reasonable to assume someone hacked your account, changed your info and then called for the tickets - or passed it off to a broker to call. I would theorize the person at the airport is going to have no idea his ticket was from stolen miles.
I have had a fair amount of issues with my AA card and bogus tickets being purchased, similar to what others have reported. (e.g. Europe to Europe ticket.)
Gardyloo - what made you think to call AA or check your account in the first place?