SQL 2012 :: Explicit Columns Or NULL Foreign Keys?

I have a table called Appointment, for storing (you guessed it) appointments at a medical practice. If an appointment is cancelled, I want to collect a cancellation reason, so let's say that I create a second table called Cancellation which has a foreign key relating to the Appointment table's primary key, AppointmentID, and another column, Reason. Now, in order to indicate that an appointment was cancelled, I could include a Cancelled column in the Appointment table with a bit datatype, or instead I could infer that an appointment must be cancelled if it has a corresponding record in the Cancellation table.

It may be that it'd be better to store the cancellation reason in the Appointment table - But regardless, let's say I stick with the two-table solution described above, and I subsequently want to write a query to list all appointments which have been cancelled. If I had the Cancelled column in the Appointment table, I could simply query for all records in that table where that column's value was FALSE. If I went the other way and DIDN'T have a Cancelled column, I could instead write a query joining the Appointment and Cancellation tables to return all records in Appointment with a corresponding record in Cancellation.

That latter method, whilst slightly more complicated because it involves joining two tables, seems to me to be the most normalised. Instead of storing the fact that an appointment is cancelled in two different tables, that fact is only stored in the Cancellation table. Would there be a performance hit in using the two-table, 'inferred cancellation' method rather than just having a bit column in the Appointment table? Would that performance hit be enough to persuade you to use a Cancellation column in the Appointment table instead? And what about if I were to apply that method to other things associated with each appointment, e.g. Is it completed? Is it chargeable to the client or an insurance company? Is the client and in-patient or out-patient?