Call your credit card company and demand they issue a chargeback for a fraudulent order. It's clear you were not shipped what you ordered and the feedback you're getting from the retailer is anything but helpful. In fact they seem to be making you jump through hoops.

One of those things usually happens in this case. You either get the money back from the credit card company quite quickly, and/or the credit card company's inquiry makes the retailer jump to attention very quickly and issue a refund themselves.

You may have to sign an affidavit for the CC company swearing to your claim.

Seems pretty clear someone in their warehouse has a shiny new D80 and their inventory system is missing a lowly MP3 player. I'm surprised they didn't just stick a brick in the box.

[edit: don't let spellcheckers automatically correct everything. ]