This is exactly what happened to me, due to the Anthem breach.
Here's a hint: call the IRS at exactly 0800 ET, when the lines open. I waited on hold for about 2 minutes, and it took approximately 45 minutes to complete the process.
NOTE: Check your junk mail carefully. I detected the fraud because a 'Green Dot' prepaid debit card arrived in the mail. The fraudster had purchased a generic card retail with $10 loaded on it, as the IRS, in their infinite wisdom, accepts these accounts for refund payments.
It was registered with my name and address, so Green Dot "helpfully" sent me a personalized card.
I froze the card, but the fraudulent return had already been filed. Fortunately, the IRS was unable to make the (fraudulent) refund payment to the (now frozen) debit card (and even helpfully sent a letter about it). So I screwed the fraudster out of $10.
I've been told I might see my (legitimate) refund in 6 months.