How do I access someone else's return I file for them under my user name

[taxlady28]

If you used your online account to prepare more than one return you overwrote the first one and it is gone.

[xmasbaby0]

When you use Online TurboTax, you get one return per fee.  Each return needs its own account and user ID.   If you use the same account and user ID for a second return, you overwrite the first one and lose it forever.

Or did you create an account and user ID for the other return?

Many people have multiple TT accounts and forget how to access them.  Log out of the account you are in now.

Account Recovery

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