[Stratoscope]

> 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...

[HDBaseT]

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).

[userbinator]

It might've been off when packed, but all the vibration turned it on at some point.