In the current store, Arclight Varus appears between Bioforge Darius (also misplaced) and Blight Crystal Varus when ordered by Release Date. (Presumably due to being tagged as having a release date of when the champion was released, rather than the date of the skin)

Actually, looking again, it seems several skins are misplaced. Almost all of the Halloween skins are together, but Xerath's two release skins are before most of them as well.

Is the skin no longer in the store?