in order to close this issue i want to make some statement.
1. since there is an email address in the business card that he has given me, i wrote an email to his company.
2. maybe, his company called his attention because he started negotiating after the email was sent.
3. he gave me a number to call, he said his partner's number.
4. his partner promised to return the money.
5. finally, the money was returned to me. he said he is very sorry for causing us inconvenience.
6. case closed.

thanks for all your comments.