Sprites Disappear (Permanently)

I was working on a big project for one of my classes. I had just recently finished the main game, all I needed was to make an ending cutscene. I opened a new scene, and saved the unfinished cutscene, but when I returned to the main game, every sprite which was previously working was gone. Now all the costumes read "untitled" and show nothing. What can I do to either get the sprites back, or revert save to before they corrupted.

Have you tried File -> Open -> Click on Project -> Restore?

It worked. Thanks. I only lost menial progress.

You may be able to recover a previous version in the open project dialog.

However, the first thing you should do now is export the project to a file so you can keep a backup of the broken project with all your code.

To recover a previous version, open the "Open project" dialog in file download > Open. Then select your project, and click Recover.

This just happened to me for the second time!

In my case, all the costume image data is gone but the names remain. I don't know what caused it. I think it was just clicking the green flag. I have some lists that are storing every sprite, sometimes erroring because deleted clones were trying to be accessed. But nothing I would think would cause the the render to erase all images!

The first time this happened, I reimported every costume manually and crossed my fingers. I can't keep doing that. Is this a bug?

Recovery in not an option, because the last version is too old. (Yes, I'll start saving more often.)