Not everyone has a IRS pin and only you and the IRS would know that you have the PIN assigned to you. It would a potential security risk if the IRS divulged to Turbo Tax, or any other company or individual, which individuals have IRS PINs.
Consider this a test of the security benefit of having a PIN. If someone other than you had attempted to file a return with your tax payer number (soc. sec) and without the PIN, it would have also been rejected. So, the in this case the process worked as designed.
