Any epithet ending in -ensis or -ense gives a hint to the geographical location where a species was first recorded by Western science, e.g. yunnanense (a plant found in the Yunnan province of China), canadensis, missouriensis and so on. Sibuyan is a 445 km2 island in The Phillippines, and a precious place by the sound of the Wikipedia entry: “In one study, the National Museum identified 1,551 trees in a single hectare, with 123 species of trees, and of this number, 54 are found nowhere else in the world”. Considering this, it is no surprise that this species was only scientifically discovered ten years ago, and the name only officially published eight years ago: Nepenthes sibuyanensis, A New Nepenthes From Sibuyan, A Remote Island of the Philippines (Eric, thanks for the link as well).
The family Nepenthaceae is restricted to southeast Asia, northeast Australia, Madagascar and some of the islands in Oceania. Like other members of its family, Nepenthes sibuyanensis is an insectivore. The Botanical Society of America has an excellent summary page on Nepenthes and other carnivorous plants.