You don't get ice unless the temperature has been freezing for a decent amount of time. Black ice is the worst, called that because you don't see it. In ice you'll almost always get understeer first as a clue that it's around. Ice can linger if it's in shade or foggy conditions though fog usually means cloud cover and that usually means it stays above freezing.
My guess would be more along the lines of something like a fluid (oily) spill that's unsettled the rear end.
Ive been humming and harring and figuring out what could have possibly ended up happening.
My theory is thus.
The road is a 70kmph road.
The mountain is popular for hoons because even at 70kmph the mountain is a dangerous, challenging drive. (aka drive hard, no chance of being got for speeding).
I entered the corner at roughly 60km, a little below I'd wager, and felt the weight of the car go 'odd'. I can't explain how, it was just 'wrong'.
Clearly it was too fast for that corner, despite driving that mountain nearly 4 times a week.
This is where I have to start guessing;
Being a right hander, the rear would have overtaken the front by swinging left
I remember countersteering it and jumping on the gas (FWD, trying to pull it straight, I've done 2 skid control days, and 2 defensive driving courses).
I don't remember actually getting any traction, and I know for absolute fact that DC5's have a horrible counter lock.
Long story short, the front of the car clearly went off the cliff first, and nearly straight, as it was unharmed (so must have been a 4 wheel diagonal slide at this point)
The rear quarter collected a tree and managed to stop me falling off the 7m drop at the edge of the cliff.
Theory 1: I fucked up beyond description
Counter: The person behind me said they didn't see me do anything odd, no sudden braking or jolting steering.
Theory 2: Something was on that road. It managed to unhinge my Pirelli P7's, which is quite a feat; even doing handbrake turns on wet grass, they want to hold.
It had JUST started spitting rain, so, there's always that....
Theory 3: One tire was hissing to flat as I got out of the car. I didn't hit anything with that side of the vehicle. It's possible I had a tire let go.
I'll never know. But the loss of my car still hurts. It meant the world to me. My escape from the demons in my head late at night.
Ah well, just gotta buy a new one ASAP.