You can see if you can open the last worked return from the 'Open Recent' under File menu.
To answer your Qn. 2, its always a good practice to save frequently while working on the returns.
As for the issue itself, Intuit is yet to fix the issue or whatever cookie they have in the registry is not removed and as such I keep getting this error whenever I open the TT. This was reported by me during last year return filing working on TT-2019 but I still see it in TT-2020 version also. What I do now-a-days is just close the window and do't click on Report it.
