Q:

How to express an appointment "has happened"?

Let's say there is an appointment between John and Peter, scheduled for yesterday at 7am.
An appointment might be "cancelled", which means that it didn't happen.
But, what word(s) would you use to describe the appointment was "completed" (i.e. John and Peter met yesterday at 7am).
Is it right to say "Did the appointment took place?" or "The appointment happened"?
Note that I'm interested in the point of view of the appointment itself, not the people involved in it.

A:

*Did the appointment took place?

No, not like this. 

Did the appointment take place?
  Yes, it took place as scheduled.

(Did took is simply ungrammatical.)
Another option is to use "meeting"  instead of appointment.
Strictly speaking, there was an appointment to meet, so if the appointment does not get cancelled, the meeting will take place.
I dare say that from a purist point of view, that is certainly preferable, as the appointment itself does not take place, but whatever the appointment was for might or might not happen. An appointment is an agreement to meet. 
So even better:

The meeting took place as planned.

Or if the appointment got cancelled:

That meeting never took place!

