Well mate there is very little you can do. . . Once you have willingly transfered your money over to someones account it is legaly theres.
There is no point going to the bank because the person who own's the account hasnt broken any laws unless he was bound by a legal contract of some sort.
My mother works in a bank and she explained to me that this sort of thing happens alot and there is absolutely nothing that can be done.
The safest way to buy/sell goods interestate would definately be via C.O.D(Cash On Delivery). Even so, you may turn up to the post office and end up paying for an empty box.
Once again. . . It would be very hard to get your money back. . .
It's a quite risky business buying and selling via the internet.