Hopefully this is just some sort of error. He did seem genuine, and saw a U.S market for the tablets that he could fill. He also said he ran another web retailer, maybe try and contact them through that:
Foscam.us - Wireless IP Cameras
I don't know how you paid for it, but you could contact them and have them stop payment on that purchase. Then send Zenithink.us an email telling them that you have stopped payment.
If you get a refund, there is another U.S. seller of this tablet, Flatcomputing.
Flat Computing, LLC - FlatPad A10
i cannot personally vouch for this seller. But it is much cheaper than Zenithink.us, and it appears that there is no shipping charge either.