The IRS Form 8879, IRS e-file Signature Authorization is not used by TurboTax. Your tax return is self-prepared so the form is not needed.
You can use the Electronic Postmark Report which has the date/time the tax return was transmitted and the date it was accepted by the IRS, if accepted. The Report will be included in the PDF download if the online editions were used.
To access your prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the section Your tax returns & documents. Click on the Year and Click on Download/print return (PDF)
If you used the desktop CD/Download editions installed on your computer, the only copy of your tax data file and any PDF's will be on the computer where the return was created. TurboTax does not store online any returns completed using the desktop editions.
Or go to this IRS website for free federal tax return transcripts - https://www.irs.gov/individuals/get-transcript
