I found this as well when I got my Dragon II- it had a part that didn't fit the artwork, and also seemed like it was missing something as well. I was right- it was missing the thigh sprue! I assembled the rest of the mini (as a Dragon II), placed the torso/arm assembly on top of the foot/shin assemblies, and put a sticky note on a popsicle stick to make a sign asking Melissa at IWM to 'PLZ SEND LEGS FOR OL' STUMPY'.
She did indeed- along with a second Dragon II! So naturally the second one became a standard Dragon. It's a hell of a lot bigger than the original Dragon mini, obviously, but it's a great mini- big fan of it, considering getting another one in fact. I highly suggest it.