Watch the part of the video where the two guys are trying to break into the safe. One of the guys uses a stethoscope to open it. As he walks in, he still has the stethoscope around his neck. Then, when that guy is about to pull open the secret compartment in the drawer, he still has the stethoscope around his neck, and as soon as he pulls it out, the focus of the camera switches to inside the compartment where the ruby is kept, but the guy no longer has the stethoscope around his neck.