Something like this happened to us recently, but it was a mistake:
Prior to a weekend trip, my husband bought (online) a 7-day fishing license for another state. I knew that he did it.
The next day Discover called me on the phone, but the spokesperson sounded suspicious to me: he could barely string two words together; in short, he sounded like a slack-jawed idiot. He asked me if I'd made any boat-related purchases lately. Nope, we don't own a boat. (Little did I know that a SC fishing license shows up on the CC as a boating/fishing license, and he never used the word fishing.) He told me that he thought someone had used my husband's card inappropriately, and he was going to cancel the card. I was sure that he was a scam-artist, so I basically said nothing to him. I refused to give my husband's mother's maiden name, etc. I thought it was odd that he didn't ask for my card number, but I figured this was the "warm up the victim" call, and he'd be calling again later for the number.
This call happened about 10:00, and I knew my husband was coming home for lunch, so I just took down Bozo's number and did nothing. Well, that was a mistake. At noon, my husband made a quick stop at Bass Pro Outlet to pick up some fishing items . . . and his card was rejected. The slack-jawed idiot really did work for Discover, and he had cancelled my husband's card.
My husband came home mad as a wet hornet because he'd been embarassed to be unable to make a $20 purchase, completely ignorant of my part in the whole thing. We pieced it all together: he made the purchase online, and Discover was suspicious because it was an out-of-state thing. I didn't recognize his purchase because he man just said boating.
I don't think this necessarily means that Discover is monitoring its clients purchases well though. My husband regularly travels to Georgia, Florida, Louisiana . . . even out west. And he uses this card everywhere. Just don't buy an $11 fishing license in SC.