The IRS has over $917 million in refunds available for taxpayers who failed to file their original 2009 returns, which would have normally been filed in the 2010 calendar year. The deadline to file for 2009 is April 15, 2013. The IRS allows a 3 year window to file a return if you are due a refund.
The IRS will hold your 2009 refund if you have not filed your 2010 and 2011 returns. So if this situation applies to you, your best bet is to get all your years caught up. Unfortunately, past year returns cannot be e-filed at this time; you must file paper returns.