NOPE. I had the exact situation a couple of years ago. Delete and start over! No amount of clearing e-file info will remove the "this return has already been filed" tag Lacerte sticks on it.

Mine was not so enormous, so it wasn't that bad to start over. The only consolation I have for you is that e-file is closed until mid-January anyhow, so plenty of time to get it done and point fingers at the IRS.

For next year, copy and rename before e-filing, and it should work okay.