Whilst accepting that "anyone can make a mistake" I struggle to see how this happened. Even on the poor quality image posted above 20L is immediately obvious to someone who has never seen the place before, taxiway C looks nothing like a runway to me and additionally is not immediately adjacent to 20R. I've looked on Google Earth and again struggle to see how a well marked runway (albeit visual markings, but clearly defined markings nonetheless) can be confused with a narrow taxiway adjacent to the apron.
Equally, shouldn't the jet parked on it's "threshold" have indicated some other plan of action?
Still, hardly the end of the world, is it?