There's got to be more to this than just not enough rain-x on the windshield. Did you have the heater cranked and on defrost the entuire time? Did the fogging start just after you had just started up the heater? It could have been that the heater got hot enough to start drying out the moisture in the air in the cab, causing the airborn moisture to condensate on the coldest part of the truck, the windshield. (jeez I almost sound like I should know what I'm talking about:))
When it finally stops raining around here run the truck until warm and then crank on the heater and see what happens. I know that even in my wife's Benz, the windshield will fog for a few seconds when we crank on the defrost, then the h-vac system kicks in and dries things out.
