The word "Nephilim" describes the "sons of Anak." While the "Nephilim" are never mentioned again #, the "sons of Anak" make several appearances. Indeed, in Joshua 15:14, they are named: "And Caleb drove out thence the three sons of Anak, Sheshai, and Ahiman, and Talmai, the children of Anak." (See also Judges 1:20.) As the Nephilim appear to be only three individuals, it is highly unlikely that their bones will ever be recovered.
In addition, while "Nephilim" is generally translated as "giants," it is unclear whether this translation is correct, especially since the word is so rare. (Granted, in Modern Hebrew, "anak" means "giant," but that could simply be because of this verse.) Other translations have been proposed. As the JPS edition of Deuteronomy states,
The exact meaning of "Anakites" is uncertain. Some take it as an epithet meaning "long-necked ones," based on Hebrew 'anak, "necklace," and its Arabic cognate meaning "neck". Others relate it to names of people or places in Canaan or across the Mediterranean containing the element 'anak or to Greek anax, "nobleman".
In such case, they would not be giants, and thus, would not have special bones waiting to be found.
( # The Nephilim make one other appearance, in Genesis, where they are described as the offspring of the "sons of God and the daughters on Man." Who or what this refers to is very unclear, but either way, these Nephilim are clearly not the same as the "sons of Anak.")