This is actually a Firefox bug which causes a user to lose all bookmarks if Firefox is not closed properly but thanks to a solution provided by anewmorning, you can restore all bookmarks using the smart backup feature of Firefox which automatically makes a backup of your bookmarks daily.
Here is how it goes:
- Go to run and type the following and press enter:
- In the folder that opens, simply open the “bookmarkbackups” folder. If you use multiple profiles then open the profile folder first and then open the “bookmarkbackups”.
- In this folder you will see backup of all your bookmarks that were made by Firefox automatically according to date.
- Now to restore the bookmarks open Firefox and go to Bookmarks → Organize Bookmarks. In the Bookmarks Manager, click on File → Import and select Import from File and click Next. Choose the backup HTML file and enjoy!
Alternatively, I would recommend Firefox users to make self-made backups of settings, bookmarks on a regular basis. Here is a good tool to make Backup of Firefox Settings and Bookmarks.