A battery fire should have been detected by the BMS. It would be sampling an array of temperature sensors in the battery pack multiple times per second, and any temperature out of range events would be captured. This is either a huge failure of the BMS, which should have detected the fire and triggered a derating of the motor and disconnetion of the battery from the powertrain (which didn't happen as the driver was flagged to pull over by pedestrians), or this wasn't a battery fire.