It would be interesting to see how the auditor worded the Non Conformance and to exactly which control it related. In most cases to get a NC for calling a QCP a
CCP would be unreasonable and difficult to justify. Very often the precise decision about whether something is a
CCP or any other form of control point is subjective and although the auditor may have his own opinion, you will have had much longer to do your own analyses. Every operation is different and what may be a
CCP in one may not in another.
That said, it is not unknown for an auditor to raise a minor non-conformance in a way intended to help you. For instance if your plan was basically OK but there were some areas where you could improve by looking at it in a different way.
Provided the extra NC didn't affect your grade, I wouldn't worry too much about it and view it as a positive and review it again. Of course if you are still convinced after your review that you were right and the auditor was wrong you can state this with all of your justifications when you return your corrective actions. You always have the right of appeal.