exact same thing happened to me earlier this week. bought 2100 points scratchcard, loaded em and next day my account was hacked and the points stolen.. and yup Fifa 12 (a game i dont even own) was on my recently played list.
I called MS, and they are unsure as how to refund me because it was a scratchcard and not bought off a credit card :/
Tell them to replenish your points for free for the amount stolen