I had a similar experience in a college physics class. I was reviewing my solution to a problem (maybe angular momentum?) with the TA, and they said, “I know you got the right answer, but I don’t see how I can give you credit for this when I don’t understand your solution.”

And I replied, “Is it even remotely possible I came up with the correct answer by chance?” They agreed not. “Then why should it be my problem that you can’t understand my method?”

In retrospect I was an ass, but I got credit and passed the class, so…