Slimies are terrestrial. A dark stream-dweller would most likely be a dusky of some kind. As the OP implies, NC is one of the salamander diversity capitals of the world, with much of that divided up in the mountain ranges around the Asheville Basin. The state has at least 18 species *just* of dusky salamanders. Many of these are difficult to distinguish by appearance. A combination of habitat, locality, tail shape, size, and coloration can often be used. In this case, the locality of Sapphire and the habitat really narrow the possibilities: at least three species of the Desmognathus folkertsi-quadramaculatus-marmoratus complex occur within 10 miles or so, one or more species of the D.ocoee complex, three species of common dusky complex (D.santeetlah, D.fuscus, D.conanti), and the seal salamander (D.monticola) occurs there as well. I am assuming a field location more or less south of Sapphire. Locations to the north would add additional species. I am not including duskies which are more terrestrial, any of the more brightly-colored Eurycea, any of the very large number of terrestrial Plethodon, or any species associated with lowland or still waters. Best guess overall is Desmognathus monticola, but I fully expect that multiple species were present.
I recently received two batches of salamanders from NC. One was "gray-cheeks", which were mainly Plethodon montanus, with a single Desmognathus ocoee mixed in. The other was "two-lined", which were Eurycea guttolineata with one surviving E.cirrigera, one surviving E.wilderae, and one surviving D.wrighti mixed in. Those mixes demonstrate what kind of diversity can be encountered in one habitat, and incidentally helped me determine IDs and place of origin. IE, if I identify two species and assume a single collector working in a small area, then all species provided probably came from the same localities at the same times.
