In the newer versions of Firefox there is also a bookmark.bak (back-up) file that is written everytime you close Firefox.
If you have lost your profile though, the 'link' may be gone (forever), but you may still be able to manually retrieve the data using Explore or a similiar file mangement program.
Firefox has a tendency to do that, all of a sudden, without warning. It brings up the browser and it as if you just installed it and were using it for the first time.
There is a free Mozilla back-up program (freeware download) that does a good job of backing up your Mozilla files (Firefox and Thunderbird).
MozBack-Up
It won't help with your current problem but will help in the future. It completely re-builds your profile and puts you back to where you were when you did the back-up.
I've had to use it maybe four times in the past year, which is strange for a software package (Mozilla's Firefox & Thunderbird) that has such a good reputation.
I think it was a mistake to use Windoze's Document & Settings directory for their profile location.
[Link]
