I'm really sorry to hear about this inconvenience.

Do you use Firefox Sync?

What was the timing of your previous edits? The reason I ask is that Firefox makes approximately daily bookmark backups (to a local file), so possibly if there was a backup between the time you finished your changes and the time the changes were reverted, then you could restore that backup.

This article describes how to make and restore backups. I suggest making a backup before doing anything else, "just in case":

Restore bookmarks from backup or move them to another computer

eastman228yahoo.com said

I worked for hours moving bookmarks and deleting bookmarks and today Firefox has put everything back like it was before I moved and deleted bookmarks. Why did it do this and how can I return my bookmarks to the way I put them?

Thanks for the suggestion, but Firefox saved the bookmarks prior to my changes, but did not save the bookmarks after the change. I guess I did something wrong. I did not change from the show all bookmarks, but deleted and moved individual items from the drop down screen. Thanks, I guess you did teach me what I probably did wrong

I don't know if you did anything wrong. Changes made on the menu or on the Bookmarks Toobar, or in the Bookmarks Sidebar should "stick." But maybe if you are making a LOT of changes, the Library window ("Show All Bookmarks") is a bit safer?

In some cases when Firefox notices problems with places.sqlite it can delete or renname places.sqlite to places.sqlite.corrupt and create a new places.sqlite and recreate the bookmarks for a compressed .jsonlz4 backup in the bookmarkbackups folder. A new backup is created on startup when changes are detected, so that might explain that you got older bookmarks.

Like jscher2000 wrote above, it is usually safer to use the Library for a larger amount of changes and possibly use cut and paste instead of dragging a selection with the mouse.

jscher2000 first asked you and you didn't answer. Do you use Firefox Sync?

If you do use Sync, disconnect from the Sync server before rearranging multiple bookmarks and when that process is complete reconnect to the Sync server and let Firefox stay running for awhile so that the changes can be sent to the Sync server in small batches.