It might not have been on line though. Would I have to contact the IRS for a copy?
2010? Turbo Tax and IRS only keeps the last 7 years. You can try the IRS.
You can request a transcript from the IRS
https://www.irs.gov/individuals/get-transcript
Or get a complete federal tax return from the IRS by completing Form 4506
https://www.irs.gov/pub/irs-pdf/f4506.pdf
TurboTax and the IRS save returns for seven years. And....if you used the CD/download software, your 2010 tax return was only saved on the hard drive of the computer you used or any back up device like a flash drive. It was not stored online.