I was surprised when I got my Muse bag and it didn't come with a "sleeper/dust" bag? What are you storing yours in? Mine of course is the off-white, so it would have been nice to have somewhere to protect it!
All my YSL's came with a dustbag. Make sure when they send you one they send you the correct size. The dusters come in different sizes according to the bag size. It should be black silky fabric with YSL in a shadowy charcoal grey going down the center. Good luck!