After you file

Are you looking in the correct account?   Or are you in the right account and just now discovering that your 2018 return was rejected and never filed in the first place?

  You have to access your own account and/or  print it for yourself using exactly the same account and user ID that you used when you prepared the return.

https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/01/270...

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

Account recovery

https://myturbotax.intuit.com/account-recovery/

https://ttlc.intuit.com/questions/1901535-forgot-your-turbotax-online-user-id-or-password

Or did you use the desktop version of TurboTax?  If so, the files are on your own hard drive or any backup device you used like a flash drive.

https://ttlc.intuit.com/questions/1901486-how-many-turbotax-accounts-do-i-have

https://ttlc.intuit.com/questions/1901535

If it turns out that your 2018 return was not ever filed then you can print it, sign it and mail it to file it.   You do NOT use "amend" for a never-filed return.  You can only use the amending process for a return that was accepted and fully processed by the IRS.    E-filing is closed for 2018 returns.

https://ttlc.intuit.com/questions/1900990-how-do-i-file-a-prior-year-tax-return

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.