if the roads were as wet as described from the event, then the oil will probably be on the surface of the water which would had been carried off or away from the surface run-off. if it was tar or something more resistant or tacky, it probably be on the road still.
even then, unless your wheels are soaked in oil , it will probably be washed off the grooves of your tires as your wheels rotate. It is not as thought you are on 2 wheels, its pretty hard to get affected on 4 wheels as compared to 2 wheels (riders in here will know what i mean) to be able to really cause you such a major spin.
also at what speed where you traveling at? Its hard to imagine wrecking a car so bad for it to be written off from traveling within the legal speed limit.
for a car to spin out and crash and to total, you need to be traveling at a significant high speed (definitely not your 60km/h or even 70.) and driving over oil spilled road doesn't really affect the spin as much as you think it would, again unless your wheels are soaked, or the whole road is flooded with it. I say this with experience from advance driving courses where we drove past oil spilled roads, and we were doing 100km/h, and yes we manage to stop w/o spin-outs.
i am unsure if i should be stern because of the many ambiguities surrounding what happened, but by giving you the benefit of doubt that you are telling the truth, i do feel for the lost of your car.