Continuity mistake: Dr. McCoy's medical tunic has an engineering patch on it, instead of the science patch it should have.
Continuity mistake: At the end, when Kirk and Garrovick are beamed up seconds before the explosion, Kirk is holding his communicator up to his mouth with both hands. But when they finally materialize on the Enterprise, Kirk's hands are down at his sides: no communicator in sight. (00:47:00 - 00:48:10)
Continuity mistake: On the planet surface, in the scene where the three security men walk around the rock, Garrovick has his arm up with his phaser. When the camera angle cuts to him alone, his arm is suddenly down.
Answer: Kirk was getting his physical and Dr. McCoy probably turned off communications, because if he hadn't, Kirk would have left and headed straight for the bridge, leaving McCoy irritated.