The first known collection of N. fusca was made by Frederik Endert on October 12, 1925, from Mount Kemul in East Kalimantan, at an elevation of 1500 m. It was discovered during an expedition to central Borneo by the Forest Research Institute of Bogor (then known as Buitenzorg), on which Endert also made the only known collection of N. mollis. The N. fusca specimen, designated as Endert 3955, includes male floral material and is deposited at Herbarium Bogoriense (BO), the herbarium of the Bogor Botanical Gardens. Endert wrote about this pitcher plant in a detailed 1927 account of the expedition, although he misidentified it as N. veitchii.