Rated 5 out of 5 stars

This is a great little add-on and do what it says. And it can be used for a different purpose like accidentally closing the firefox and losing all the work.

Đánh giá này là cho một phiên bản trước của tiện ích (1.5). 

Thanks for the review!
Actually, you don't need FCT for that.
I'm guessing you've disabled the "Warn me when closing multiple tabs" option. However, you can still restore the session after restarting Firefox by clicking on "Restore Previous Session" in the History menu. If you happen to use the default Firefox homepage, there's a button on it too.