If you used the TurboTax online editions and completed another tax return using the same account as was used for the original tax return, then the first tax return is gone.
Go to this IRS website for free federal tax return transcripts - https://www.irs.gov/individuals/get-transcript
For a fee of $43 you can get a complete federal tax return from the IRS by completing Form 4506 - http://www.irs.gov/pub/irs-pdf/f4506.pdf