How do you try to resolve an issue where payment is made for residential land and no deed or follow-up is given by the seller?

I bought a parcel of land from sellers on eBay (5/17). One seller is from CA and the other is from IL. I live in NYC. I paid the amount for the parcel and my cashier's check was cashed by one of the sellers. We'd been corresponding through eBay. After 60 days eBay's policy of money back guarantee was expired. They wouldn't give any information either about the sellers or the listed parcel. The 2 sellers stopped responding to my emails on ebay. Then both dropped off of ebay. I have the telephone number and address of one of the sellers in Chicago, but the person still hasn't responded. I'm not sure what the issue is with the sellers, but I'd like either the deed to the property I paid for or my money returned.