If you sent your extension in on time, it should be granted. To confirm receipt, it's easiest if you use software like TurboTax Easy Extension, since you'll get a confirmation from TurboTax within 48 hours.
If you use the U.S. mail to send your extension, you'll have to contact the Internal Revenue Service (IRS) to ask about extension status. Currently, you can't do this on the IRS website. Call the IRS customer service number to determine if your request for an extension was received and approved.