Closed Window and Lost Tabs?

[Purple Curtain]

I've had two windows open for Mozilla Firefox for awhile (I accidentally did some keyboard shortcut that split my tabs into two windows). On one of them, I had some really important tabs open. Unfortunately, I closed that window (also by accident). I restarted my computer, hoping that it would come back up, but no luck. I tried reopening Firefox, but I just got a blank tab. Is there anything I can do to retrieve these lost tabs?

[Q]

It should show up on your History tab.
Tap ALT once (for windows 7 and on) and look at History menu.
Your closed pages should be down there, if not click Show all History

[Maria]

Orange Firefox button on top left
History >
Recently Closed Tabs >

[Jodi]

Go to your history