Power loss is a real stretch to happen at the same time of communications, I understand that the coms to fail is a non-zero chance of failing, it happens. A transponder is super rare on it's own, but when they both go at the same time, protocol dictates you declare an emergency straight await (the top-side cnc). Not that it would have made a difference, but they certainly would have told the coast guard all of this. Even after waiting FAR too long IMO.
Yes indeed, but the transponder itself is a self-powered device, they are battery powered when needed and those batteries are usually no joke from the ones I've encountered, as it should be. Specific times I'm not sure. I'll link one I have worked extensively with. They are designed to be extremely fault tolerant with a lot of redundancy and fail safes.
It's genuinely extremely hard to not notice it losing power.
The fascination with the gaming controller is a bit silly.
It's not safety critical like the ability to drop ballast is. If something goes wrong with it you just kill propulsive power, resurface, and replace it. Also more engineering effort will have gone into making the controller reliable by its manufacturer than most would want to be able to justify spending creating something custom.
> The thing uses Bluetooth for mission-critical controls
Mission critical - I'm not a marine, but as I heard they did have redundancies for buoyancy. If the best of the worst happened, I would guess they would have surfaced pretty soon..