well, if you make backups, then you can at least import a version from the backup
if you do not make any backup then you might have to recreate that screen… or recreate the complete app if you have bad luck… don’t worry, the second time it goes faster…
see also MIT App Inventor 2 Tips – TWO DOG APPS
Ok, you made backups, so you can do some surgery to copy the 2 files of the missing screen from the backup to the current version of the project
Open both aia files using 7zip
Find the src subfolder and open all subfolders inside until you find the bky and scm files of all screens
Drag the 2 missing files from the backup to the current version
Upliad the modified current version into Kodular