I was spectating some setup testing, after a lagspike (my connection I think) the track disappeared, skidmarks were still visible, and it showed wrong way while the car was going the right direction. Changing camera didn't help either, finally the track became visible again after I had chatted.

I couldn't tell you why (as it happens for different reasons), but at appears as though the track textures are being preloaded again. The track textures sometimes tend to do that if you, for example, shift to windowed mode whilst out on track, etc. I wouldn't say its a bug, but possibly inconvenient.

I had it happened some times, once i can`t see nothing more than cars and skid marks

I've had that happen as well with the exact same results for the same reason (lag spike).

Yes, this BUG! kill

Happend to me too, but I think the program "forgets" where the car's position is (for displaying the track), because when the car made one whole lap (from the lag point) the track reappeared and everything was ok.

I even have a replay where this is happening... but finding it will be tough maybe impossible... i got around 300 replays and i can't remember where it happend...

I followed GForceSims001 as spectator and I couldn't see the most of the track for a while. This happened online and I recorded an MPR.
At around 2:15 in the MPR there is lag and ten seconds later the track disappears and a 'wrong way' message is shown.

not necessarily only multiplayer (check attachment)
altough I often see it also in multiplayer and it should be definitely fixed