the remote shock resevoir is an external tank that hold shock oil. In extreme cases your shock oil heats up, having an external tank allows more fluid capacity without changing the dampening characteristics of the shock. You standard car does not have this but most dirtbikes do. This is most likely not a case were it was removed from the stock shock, as it would leave the stock shock useless from the oil squirting out. If you suspension works, don't worry about it, if you are that worried, you could disassemble you bike trying to find exactly were it is, or if you have a non original shock.