When I go to Sams, once in awhile the checkout person says I am approved for their Discover branded card so this is common. IMHO technically, your wife comminted ID theft since she open a new account in your name even though he was an AU on the store card.
I think the proper interpretation is that the store forced the transaction and was the party here who comitted a fraud. The clerk could have a lot of explaining to do. Why bother risking your job for a very minor spiff?