SKU #? If you used the CD (or download) Desktop program then the only copy of your return is only saved on your computer. Both the .tax2017 file and pdf files. Do you need to reinstall the 2017 program to open the .tax2017 file?
Did you use Windows or Mac?
If you used the Windows Desktop program you need the file ending in .taxyyyy to open in it. The tax files (and PDF files) should be in your Documents then in a Turbo Tax subfolder. If you can't find them do a search for all files ending in .tax or .tax2017 etc. And check the Recycle Bin. For Windows 10 check the One Drive. Did you make any backups? Like DropBox.
If you don't have the main .tax file you might have one that starts with a Tilde sign ~ like
"~your name.tax2018". That file is if your computer crashes or your real file gets lost or deleted or corrupt so you can restore it.
Find your Tax file in Windows
https://ttlc.intuit.com/community/tax-data-file/help/find-your-tax-data-file-tax-file-in-windows/00/...
