Sorry that this has happened, but it is not typical behavior.

Firefox automatically created backup copies of the bookmarks, for details of how to restore bookmarks from a backup see this support article - Restore bookmarks from backup or move them to another computer

This support article may also be of use - Recover lost or missing Bookmarks

You can check for problems with the places.sqlite database file in the Firefox Profile Folder.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

"Not typical behavior". I think not. I am yet another person this happened to. Even if I can get them back, you've just wasted an hour or two of my time. I won't be using firefox again after I've recovered my bookmarks. If I recover them. Thanks for nothing.

You should be able to fix this easily because Firefox keeps ten JSON backups in the bookmarkbackups folder, one each day that you start Firefox.
So a lot must go wrong like a full profile loss to lose all bookmarks.

If rebooting or deleting all places.sqlite files like I posted above didn't make the bookmarks reappear then you can try to restore them manually in the Bookmarks Manager (Library).

• http://kb.mozillazine.org/Backing_up_and_restoring_bookmarks_-_Firefox