Volador, the difference is that when the case bracket is not there the spacers need to be about 8mm longer to keep the muffler in the same location on the bike.
Stokester, the photo clears it up! The spacer broke off. To me it looks like the right spacer, when you said rear I thought you were talking about the back side of the hanger.
If it were mine, I would just repair it with a short piece of 1/8" brass pipe.