If you Sign In with the same User ID and Password to TurboTax Online, you can work on your return from any computer.
The most common reason for not finding returns is signing in with the wrong user ID, which can happen if you have multiple accounts.
If you need to find an account, our account recovery tool can help you find your user ID or password.
Here's more info on How to Find a Tax Return.
If using Windows, the return you were working on may be stored in a file in the Documents/TurboTax folder on the computer that you started the return on.
I would look for a file in the Documents folder on the computer you were working on, or start a new return.
If you re using online TurboTax you can access your return from any computer or device that has internet access if you use exactly the same account and user ID. If you have the CD/download, the return is only on your own computer's hard drive. It is not online and cannot be accessed from anywhere else.
If you are using online TurboTax
Many people have multiple TT accounts and forget how to access them. Log out of the account you are in now.
https://ttlc.intuit.com/questions/1901535-forgot-your-turbotax-online-user-id-or-password
https://ttlc.intuit.com/questions/1901486-how-many-turbotax-accounts-do-i-have