Many people have multiple TurboTax accounts and forget how to access them. This may be why you can't locate your tax return. Log out of the account you are in now. Using exactly the same account and user ID that you used when you prepared the return. If you are not sure, you can try to recover that account with your phone number. Go here to find all of your accounts. One of them should have the return you're looking for.
If you don't have that information or you need assistance getting back into your account, you can follow the steps in this TurboTax FAQ here.