WOW! That’s quite a mess. It does indeed look as if the ignition point was located on the passenger seat. I don’t see a charging cable leading to that area, however.
It is certainly possible it was an iPhone as a few have burst into flame when being charged with non-Apple certified chargers that will over-charge an already fully charged battery.
The phone is sitting on his desk in his office. I may have been wrong about the plastic. It might have been what was left of the battery, touch screen, etc. It looks like two metal plates with a glob between them. The circuit board can be seen.
Shocking how much heat is generated when a smartphone melts down. Hot enough to ignite flame retardant material. Just a guess but the temperature must have been close to 1000 F to cause the widow glass to start melting. One of the UL tests is to determine when a device fails if it fails catastrophically or benignly. Clearly this phone would have failed that test.
The risks of our modern lives and batteries.