content: I think this might have been what happened.  Even the tail light looks melted.  It doesn't look like only the black parts absorbed enough heat to melt, it looks like everything plastic on that side of the car melted.  If it were that hot, don't you think the people would be having problems standing out there? The plastic looks to be already hardened in a dripping state (not actively dripping or soft) so I reckon that they parked it in one of the few spots that gets a nice large reflection from one or more windows on a building nearby during a certain time of the day.