I reckon they're absolutely fucked. Obviously, rescuers would need to find a precise location in order to try to physically recover it. It's not transmitting that data any more. Plus, with the vessel being at something like 12,000 feet, how the hell would they get that back up to the surface?
I doubt any ROV used in Oil and Gas can go that deep, and it probably wouldn't have the capabilities to recover a submersible. Saturation divers can't go anywhere near that depth, so any rescue must be hinged upon having a capable rescue submarine getting down there within the ridiculously small timeframe they have left. Hopefully the thing just got crushed under pressure and they died a quick death. Would be shit to be just sat there in your tomb, waiting to run out of air, lol.
I'd love to see what this company's risk assessment and CASEVAC plan looked like. You'd assume they had more in place than 'let's just take down extra air and supplies'.
Edit: This is interesting. I was curious to see what we have in place for situations where our military subs run into issues. Our NATO equipment can't get near those depths. The Submarine Rescue Vehicle can reach max depths of around 2000 feet. Unless they're just bobbing around somewhere, which is extremely unlikely, they are dead.
https://www.royalnavy.mod.uk/The-Fleet/Submarines/~/media/Files/Navy-PDFs/The-Fleet/Fighting-Units/Submarines/NSRS%20Factsheet.pdf
