I've never seen anything like this before. I would be very concerned...I know the electrics are usually housed in the top panel, which seems to be the bit that flew off. I would maybe get the power point tested, just in case. If it were me, I'd be wanting some answers from the manufacturer and probably would not buy the same brand to replace it. If a child had been nearby, it could have easily had a serious/fatal result.
Let us know what they come up with....could save some dramas for others.