Ok first of all leave a negative feedback to him here https://bitcointalk.org/index.php?action=trust;u=95649 and put the reference link to your thread.

THen open a scam accusation with the proper format in this board https://bitcointalk.org/index.php?board=83.0 posting proofs of the scam (it is was in PM, a screenshot of PM should be fine for most of DT members)

Last but not the least: always use escrow for your trades....

Hope it helped (if not to gain back your money, at least to not let him go around and scam again)
~Gun