BX cable in plaster by sink
You're fine

A "damp location" in the NEC is a location that's subject to dampness on a regular basis, not any location that conceivably could be damp at some point in time.  For instance, a walk-in cooler is a damp location because of condensation forming on a regular basis, and the area beneath a fixed awning will often be subject to dew (and sometimes to horizontal rain), but the bathroom vanity cabinet is a dry location even though it will get wet if the sink leaks (because a sink leaking is hopefully not a regular or normal occurrence).

This is accounted for by the definition of "Location, Dry" in the NEC:


  Location, Dry. A location not normally subject to dampness or wetness. A location classified as dry may be temporarily subject to dampness or wetness, as in the case of a
  building under construction.