I had 'open tabs from previous session" selection in my preferences, and yet after closing firefox (and turning off my computer) I turned my computer on to find that firefox had a new session with the start page. I have Session Manager now (way too late to help with this problem, but it'll help in the future). I looked at my session restore files and the js file is from today, but there's a file called sessionrestore.bak-20140212131424 that's from a little while back (that would have at least most of the tabs).

Ideally I'd like to get my tabs from yesterday, but I'd just like to get as many of them back as I can. I'm working on a Windows 8 if that effects anything.