If lost content are not in backup files, it means that between last backup file and crash, work wasn’t saved.
There’s no possibility to to recover lost data in this case.
Can’t confirm if your empty content in story board means frame content was lost or if it was just a preview bug… ?
Ideally, a “save as” before closing would have been a thing to do (but not sure it would have been a solution to not loose frames content…)
Note the Story Board is buggy.
It can generate
- really weird freeze
- weird lost of frames (no bug reported for this case…)
Did you tried to reorganize story board content?
Grum999