From the outside lookin in, it sounds to me like the ball was clearly put in your court when you were asked to send the parts back. You did not. You dropped the ball.
I can see where you would get that impression. But when he says send them to me and I ask what are you prepared to do about it? And his answer is I don't know. That's kind of a red flag to me. Could have given some idea or at least carried on conversation and come to a resolution that satisfied both parties. Is this a statement you can agree with?