Amazon lost my package

Amazon lost my package and will not honor the price I bought it.

I bought a race car bed for my son for $100 on Amazon Warehouse. Amazon is the seller. I ordered on 3/10, on 3/16 I contacted Amazon. They couldn’t do anything at the time but customer service said to ask for a replacement and they should honor the price. The bed is now $300. On 3/18, the CS supervisor said he will not honor the price. Would give me a $40 credit but I would still have to pay more for a package that they lost. What should I do?