It was never really a possibility and i expect most in the industry, both subs and rescue knew it. I'd be surprised if they ever found the sub itself considering it's size
edit: gosh, how long would it take for the thing to rust through? If/when it's found, can you imagine the inside after decades...
Kinda knew that from the start, considering the facts, the current record for deep sea rescue is what 1500ft or so, this vessel is roughly 12,500 ft down, not a hope in hell, no way for the passengers to escape the vessel and even if they did they'd be dead instantly due to the pressures that far down something like 380 bar or so, then of course theres the nitrogen issues so they wouldn't be able rise fast. Basically its a cluster **** of issues with no safety or backups in place for the passengers.
I cannot possibly imagine the horror those on board are dealing with, specially the civilians. For all we know the former military person may have offed the rest to preserve oxygen for himself. If 5 could do 96 hours, 1 can do a week or more.