You have to call Amazon. We went through this 3 days ago. Ordered a new practice drum pad for the 17 year old. Didn't show up when it was supposed to. Reordered, showed up next day. Day after that, original order showed up. Box was empty. Stamped, "received without contents". Mrs. smokeywolf called Amazon (I think you have to email or PM them on their website then they call you). They said, "no problem, we'll credit your account".
Don't know if this made any difference, we've done tens of thousands of dollars in business with Amazon, both as buyers and sellers.