How can I recover tab groups if I accidentally hit "X" instead of "Exit"?

Question

Hello,
I had about six tab groups open with a total of 100+ tabs and accidentally clicked on the "X" at the top-right (I'm running Windows 7). The entire program closed without warning me that I was closing multiple tabs. When I restarted the program, only my most recent tab group was restored; the rest are gone. As you can imagine, I really want to get the rest of my tabs back.
How can I restore the rest of the tab groups?
Also, how can I make sure that one of following things happens?:
- Disable the "X" button
- Replace the action of the "X" button with the "Exit" function, such that if I accidentally click the "X", Firefox will exit and save all my tabs for the next session
- Enable the warning about closing multiple tabs, before the tabs are all closed
Thank you for your help!

Answer 1

Thank you for the response, cor-el. Yes, I did look in recently closed tabs and windows. However, the recently closed windows section did not contain the tab groups that I had open previously (it only had two pop-up ads which I was not looking for), and the the recently closed tabs section only contained tabs from one of the tab groups.
All of the "restore from last time" and "warn before closing" options were enabled prior to my accidental close-out, but neither option is working as it should.