I would suggest that the box was dropped from five or so feet and landed on the bottom flat surface, hence no damage to the packaging. I had the same thing happen to my D-28 in a different circumstane (an airline) and that was why. Call the supplier 'soon as' and explain the circumstance. I was in tears, but stay cool and see where that goes. Take pictures--clear ones--so the supplier can see the damage. I doubt that's the first time it's happened so it shouldn't be a surprise to them.