he payed with western union i think
Excuse me, but your friend is really stupid if he/she fell for that. If an online-store or person asks for payment through Western Union you can almost guarantee that it is a scam. That's because it's the most anonymous transaction possible.
If you ask them whether you can pay with credit card, account-to-account transfer, Paypal or anything of that sort, they will give you hundreds of excuses as to why that is not possible. The real reason is: They would be trackable.