You would be told of any offset that was filed. HOwever, notice sometimes does not come until just before the offset has occured.
You should check the status of your return at: https://sa1.www4.irs.gov/irfof/lang/en/irfofgetstatus.jsp
Then contact the lender and ask them if they are referring it or do you still have a chance to pay this off.
This is a dilema, I know. Unfortunately, if the offset has already been filed, then there is nothing you can do at this point. Even if you pay the debt, it takes time for the agency to successfully withdraw the offset. Also, it may not be that easy, because even though you pay the debt, the offset can include the cost and expense of getting the legal documentation to refer the debt to the offset program. At least they will want to recoup those expenses.
My best advice, to avoid a penalty with the IRS and give you the time to act, is to file an extension. You must include a small payment with the extension, even if you expect a refund. I recommend a 50 dollar payment. This will give you until August to fix things up.