How did you pay?
If by Paypal then search on facebook using the same e-mail address and it may bring up his profile. Also search on google for both the e-mail addy and the bit before the @ sign – see if he uses that as a username anywhere. Bear in mind he could be using a hijacked account (unlikely though).
If you find his profile, save a copy of it, and also a copy of his entire friends list, before you contact anyone.
If paying by bank transfer then you can do a check on the sort code to find out roughly where he is.
If by cheque then cancel it.
If the mods are feeling especially kind they could hand over his e-mail address he used here, plus (not sure if they would – bit dubious) his password – chances are he uses the same one elsewhere – you might be able to find out more details about him if you log into his webmail.