I don't know what happened, but I suggest making some backups ASAP. Do not exit Firefox, or if you closed it, don't re-open it.

(1) To open your profile folder...

If Firefox is still running:

You can open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, click the "Show in Finder" button.

If Firefox is closed:

Use the steps in this article to find your most recently updated profile folder: Profiles - Where Firefox stores your bookmarks, passwords and other user data

(2) Copy out session history files

In your profile folder, scroll down and double-click into the sessionstore-backups folder. Save all files here to a safe location, such as your Documents folder or Desktop. If not too much time has passed, we may be able to use them to recover your lost tabs.

(3) What files did you find?

The kinds of files you may find among your sessionstore files are:

• recovery.js: the windows and tabs in your currently live Firefox session (or, if Firefox crashed at the last shutdown and is still closed, your last session)
• recovery.bak: a backup copy of recovery.js
• previous.js: the windows and tabs in your last Firefox session
• upgrade.js-build_id: the windows and tabs in the Firefox session that was live at the time of your last update

Could you take a look at what you have and the date/time of the various files to see whether you think any of them would have the missing tabs?

show in finder: reveals a folder underneath profiles with a long number/alphanumeric string. nothing else. In this folder there are many things but no sessionstore-backups.....

second page...

I have never seen a profile folder that does not have a sessionstore-backups folder!

Did your Firefox very recently undergo a Refresh? Please check your desktop for a folder named Old Firefox Data and click inside to see whether you have recently updated session history files in there.

well this is odd. Given the help you have been I figured I was out of luck.....and started managing my bookmarks, basically to start over again. Well, when I went into the bookmarks and started deleting all the nonsensical links from the desktop, (I am on my main system my laptop doing this), I noticed that after I deleted a few my OLD ONES were now on screen. Basically firefox APPENDED my links to the end of the chain.....they were alwayys there....I never clicked the double carrot arrow because it did not occur to me that BOTH system would be conjoined as it were....so i think all is well.