If you're getting 0 signal after a thunderstorm, that means that either the dish was moved by wind, or something got moved in front of it, like a tree. We had a thunderstorm to the south last night that blanked out the signal for a good 10 minutes, but came back as the storm moved to the east. You could almost track it with the signal meters.
The basic procedure is to loosen the bolts and move it around until you reacquire then tighten them up but I'm sure someone with more experience will point out something more useful. LNB didn't get hit by lightning or anything did it?