Mustache Lips Makeup

I had guessed it was Sam, but for that to have been the case both the blue and the red box would have been opened but the green one left untouched.

Every once in a while Conrad drops a hint that Sherman Holmes is completely insane, while still excellent at deductive reasoning.

I also guessed Sam - I figured that since Dora had been out of the room, she had no way of knowing it had been put back into one of the boxes, and so the reason the thief went through all of the boxes was that he was colorblind (an overwhelmingly male affliction), and since a colorblind person would hardly make a good jewler, that would rule out Buddy. (I know, I overthink stuff...)