I did not e-file or complete preparing my return, why does it show ready to mail when I logged in today? There was a button "I'm not done" which I remember NOT CLICKING.

If you completed the File section of the program but did not e-file the tax return then the status of the return will show as Ready to Mail.  Meaning that you would have to print and mail the tax return.

If you have to complete the tax return and want to e-file the return, see this TurboTax support FAQ - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/change-mail-e-file-turbotax-online/L0zDlGPhq_US_en_US