Sorry to hear about this problem. Firefox usually restores your session after an update automatically. But if you were using exclusively private windows, then you are out of luck.
For more control, why not modify the automatic update setting? Here's how to find it on the Settings page -- type update into the tiny search box to bring that section into focus. From that point, it's pretty obvious what to click next:
(Note that this might not work on Linux because usually your package manager handles the updating.)
Finally, if you want assistance mining for old data, try posting this problem on the Mozilla Support site. They have a team of support volunteers to troubleshoot malfunctions with your currently installed version of Firefox, while this site is focused on idea submissions for future versions of Firefox (looking ahead anywhere from 8 weeks to many months). Here's a link to the new question form (for Windows/Mac/Linux): https://mzl.la/3y1vQUQ
