How can i reopen an unsaved incomplete turbotax file?

Did you start it in the Online version or do you have the desktop program installed?  You need to have the data file ending in .tax2019 and the 2019 Desktop program installed to open it.  Are you on Windows or Mac?

After you install or reinstall the program you may have to download the state program.  The first thing to do before you open your tax return is to update the program and install any state programs you had. Then open your file. So you first might need to start a fake return to be able to download the state program (go to FILE - NEW).

If you used the Desktop program, the .tax files and pdf files are usually in My Documents in the Turbo Tax folder. Or search your whole hard drive for all files ending in .tax or .tax2019. And also look in the Recycle bin, people are saying they found it there. In the Windows Desktop program you have to make sure to manually save it yourself, although it should ask if you want to save when you exit or start a new return. In Windows 10 they might be in the One-Drive area. Check your Recycle Bin and any other places you use or backup to like Drop Box or One Drive or any cloud backup services.

Find your Tax file in Windows
https://ttlc.intuit.com/community/tax-data-file/help/find-your-tax-data-file-tax-file-in-windows/00/25926