Originally Posted by
LaTeeDa 
Perhaps he listened to your story in order to determine if the appointment was missed due to "circumstances beyond your control." Perhaps, after listening to your story, he decided that the missed appointment was caused by a series of choices, not beyond your control, and therefore payment for the appointment is a consequence of your actions.
I agree with this. I'm guessing if your car had broken down and you'd called him at the time he'd have waived it. But I can see why he charged you under the circumstances.