I had the same thing happen two years ago. It took more than a year to discover the problem, and another year for the IRS to accept my return.
At the end of the TurboTax process, there's an opportunity to make copies. Before those screens come up, I did not elect to file the return at that time. By the time I saved copies and entered my drivers license, etc. on subsequent screens, I thought I had filed but never actually did file electronically.
After properly transmitting the forms to the IRS at the very end, you should see a confirmation screen. You will also get an email stating that your return is being processed. Without these confirmations, your return will not have been transmitted to the IRS.
