As a customer I would probably be upset; however, I also believe that as a customer I have a responsibility to make my wishes known to the retailer.
Point in fact. I recently purchased two laser cut wood kits to build for my brother-in-law's train layout for Christmas. The online retailer inquire if I was aware that I had ordered two different scales. I replied to him immediately as to delay would mean a delay in receiving my items.
Believe you handled the matter professionally.
Betty in Colorado