When you use desktop software, all the data files and any PDFs you saved are stored locally on your computer and/or on any backup media. They are not sync'd and stored in an online account.
If you didn't save the data file or any PDFs, there's not a way to retrieve them.
You can download a free 2015 tax return transcript at the IRS website below. If you don't qualify for the immediate download, you can order one to come by postal mail in 5-10 days.
http://www.irs.gov/Individuals/Get-Transcript
A full copy of the actual return from the IRS costs $50 and takes several weeks.