The police could care less. That is a bluff and a lie. Besides, you have not done anything wrong.

Immediatly file a complaint with eBay. If you paid with PayPal, file a dispute with them. If you paid using a credit card, immediately file a chargeback against the seller. Don't allow the seller to play games with you or stall.

You should certainly be aware of what was being sold and what you received. You know, there are photos and so forth on eBay. This part of your story though is very flaky. I hope you have the tracking number and info on sending it back.

Although you should tell us what state you are in, state law really is not going to have anything to do with this. This will be handled with eBay and the payment company. Nobody is going to sue someone in another state over 500 bucks.