RE: What could I have done?
Got a couple questions for you. Do you wear your binocs around your neck and possibly inside a jacket or coat? That would keep the binocs warmer than the ambient temp and keep them from fogging. Same thing with your scope, it seems it is colder than the ambient temp. somehow, get the temp of your scope warmer than that ambient temp. Warm the ends with your hands, or even use a "hot hands" to warm it up some. It's the same thing as glasses. when they are warm and you go out, they don't fog. but if they are cold and you go into a warm house, they will fog. Your scope works the same way. Other than that, I'd hate to say it but you could have lost the inert gas inside of your scope, heaven forbid.
Russ