After updating Mozilla Firefox from version 27.1 to version 28, lost all the last saved session

I've lost the whole saved sessions again tonight after a blackout in the whole city this time, for the 3rd or 4th time since I started using it and still no way to recover anything. I see no answer is ever given about this issue in months. We are left all alone without answer.
The support team should give us an answer quickly, my saved sessions are very important to me, it's vital for me to get them back!
If you Alex managed into solving this issue please let everybody know. Thanks so much...