Did you get any notices in the mail from the IRS stating they over paid you? The only way they would take out money is if there is a discrepancy in the amount of money coming back to you.
How much was your return supposed to be? When you say you were paid by a cashier check, what do you mean? Do you mean the check which comes from the IRS? With printed information on the check?
I would call or write them to clear this up, it sounds like an error on their end. Unless you were not due a refund and they made a mistake.
Hope this helps.
