Charge all you want; they won't pay.
Also, you'll poison the well, the whole relationship between you
and them will go down
the tube, you'll never have another comfortable conversation
with the doctor, and you'll
have to start looking around for a new doctor, who won't know
you.
Most likely, the doctor didn't cancel because the foursome ahead
of him was playing too slow.
He canceled because another patient ... either in his office or
in the hospital ... was in extra
bad shape and needed some more of his attention at that
particular time. If it had been you,
you wouldn't be too happy if he had said to you "Gee, I'd really
like to stick around and
help you start breathing again, but ya see, I've got this other
patient coming in and I don't
want to disappoint him."
Let it go.