The phone app is an access point for Turbotax Online. Tax returns prepared using Turbotax online can be accessed from any computer with a web browser, and do not "live" on your device itself.
If your current Turbotax Online account is missing some years, it is possible that you had a different account (different user name, password). The other expert has given you some suggestions of how to find those accounts. In some cases, you might be asked to pay to unlock old returns, if they are contained in an account you have not used recently. If you have been using a different account, you may be able to call customer support to get them to unlock the old account for you.
You can also obtain copies of the returns you filed from the IRS.
https://www.irs.gov/individuals/get-transcript
