That's not exactly bad news now (if) they've focused the search. Regarding the ISIS, there are many faults possible with the device. Could it tumble? Theoretically it is a solid-state device and not prone to that, but in a severe upset anything is possible. A power interruption also may corrupt the operation of the device. I've had one fail in flight giving a generic FAULT code and a blank screen. Who knows but the engineers all the fault modes possible...