Turbotax maintains copies of people's tax return by their account number, not social security number.  If someone else did your 2015 tax return, it would have been under their account number and they alone would have access to your return.  You will either have to go back to them and ask them for a copy, which they were legally required to give you anyway, or follow the Link below to request an official transcript of your 2015 tax return from the IRS.

https://www.irs.gov/uac/newsroom/request-a-transcript-or-copy-of-a-prior-year-tax-return