FTR, coated rebar fails far worse and usually far sooner than coated rebar. Because it rusts behind the coating anyway, it just ends up de-bonding from the entire application (the coating is bonded to the concrete, not the rebar, the rust debonds the coating) and then the rebar has no resistance to extraction forces at all. Uncoated just swells, but stays fully bonded.

It was a good idea in principle, but fails in execution because it is impossible to keep the coating from being damaged during install. Only stainless rebar (yes, it is a thing) actually prolongs the service life in high chloride ion environments.

ETA: That said, I doubt salt has anything to do with this collapse. It is most likely something geologic, such as a sinkhole as suggested or a number of other possibilities.