The Blowdart Sniper Club was, as the name states, intended to be an alternate weapon for the Blowdart Snipers in Blighttown, for when the player was in melee range, and as a result, was also intended to be one of their dropped items.
The most interesting aspect of this weapon is that the Blowdart Snipers are able to use it when forcibly equipped through third-party programs; that is, the weapon has its own moveset when they attack with it. However, the only reason it is not used by the Blowdart Snipers is because, within their programming, they are defined as being enemies who cannot switch weapons.
Due to its nature as cut content, the Blowdart Sniper Club is simply a texture in the game files. This means that even if the player modified their save file, it would not have its own stats anyway, as an existing weapon's model has to be overridden in order to 'obtain' it. Hence, the weapon can only be seen by those who are modifying the game to use its model.