When did you prepare and file your 2018 return?
If you prepared and efiled it by Oct. 15, 2019, did you get two emails soon after filing it? The first email would have said the you submitted your return. The second email would have said whether it was accepted or rejected. If it was accepted, the IRS received it. If it was rejected, you had to fix the reason for rejection and resubmit it or print and mail it.
A 2018 tax return could not be efiled after Oct. 15, 2019.
If you chose to print and mail your return, you had to print and mail it yourself. TurboTax does not print any mail it for you. TurboTax has no way to know whether you printed and mailed it or not.
It's common to end up with multiple accounts. First LOG OUT of whatever TurboTax account you're logged into right now. Then use this TurboTax account recovery website to get a list of user ID's for an email address. Run the tool against any email addresses you may have used
If you used the Desktop CD/Download program then the only copy is on your computer and not saved or stored online.