I hope this is an isolated incident, but maybe the days of the cardboard thin smartphone are over. If the internals get warm, they expand and if no room to expand, it may be pinching the plates of the battery causing the battery to short out and explode. They could easily make the phones 50% thicker and I wouldn't mind.
Nothing quite like cladding something that can't dissipate heat fast enough with a thick layer of insulation. It might be interesting to see if there's a performance drop associated with self-preservation when things get hot.
Perhaps the next hardware innovation will be a forced air cooling system.