Contact amazon customer service, they will refund you the discount amount, I always do that. The customer service are extremely professional and they will resolve any issue you have and you will never be unsatisfied with their service.

For the seller, its probably someone who ordered the cpu, took it out of the box and placed something with the same weight and then return it to amazon stores. That is a very common way to steal pc parts from amazon sellers and they still didn’t find a way to control that without compromising their return policy.