How do I restore the tabs in my Firefox session after having accidentally clicked on 'start new session'?

I have Mozilla Firefox 3.0.8 and don't believe I have any "session manager" add-ons. As a possible solution, I wonder if session manager add-on can recreate a session(s) ( I had 3 browser windows sessions) retroactively?|||i think you just need to activate the function in tools, and it will do that from now on.|||i'm not sure if this will work in your situation, but click on history at the top, and then recently closed tabs.