> it was probably in checked luggage
Which would violate FAA regulations if it was powered on (as it obviously was):
"When portable electronic devices powered by lithium batteries are in checked baggage, they must be completely powered off and protected to prevent unintentional activation or damage."
https://www.faa.gov/hazmat/packsafe/portable-electronic-devi...
It might've been off when packed, but all the vibration turned it on at some point.
How exactly do we know it was in checked luggage vs carry on luggage compartment.
Without tools, its not exactly easy to point-point a Bluetooth signal. Nor are passengers meant to be roaming around the aircraft whilst in flight (i.e to access carry on luggage compartment and turn it off).