No, they didn't survive for years. They died after a short time, but their ranks were continually replenished by fresh ants falling from a colony above.
> "In total darkness, they have constructed an earthen mound, which they have maintained all-year-round by moulding it and keeping the nest entrances open," researchers wrote in a study in 2016, noting these ants are "a far cry from a fully functional colony".
> They were not reproducing, though. Instead, the population was being replenished through sheer accident.
Fascinating.