First of all, your pleas are misguided. You're more likely to get something done if you contact support directly. Posting in General Discussions is going to accomplish nothing. At most, you might be greeted with unneeded hostile, aggressive posts, such as the ones above.

Second of all, if this was done via Steam's trading service, OOO has no power over this.

Thirdly, the track record of getting scammed in this game results more often in not in the scammer being reported (probably getting a warning, or even temporary [or if the offense is bad enough] permanent ban), and the scammed getting no reimbursement.

The way you word this makes it seem as though you were ignorant to the value of the items you offered. This is part of the problem. More often than not, people will take advantage of the ignorant if it is convenient for them. (For example: merchants overpricing Skolver coats with Elemental or Shadow Max under the guise of selling a viable Lockdown set to someone who doesn't know how Lockdown's mechanics work.) If a merchant sees they can get away with paying 10k for something worth 200k, they won't hesitate. The only thing you can do is be more careful next time.

As mean it was for the guy to shark you(for those who don't know, sharking is the tf2 trading term for ripping someone who doesn't know the price of an item off), it was partially your fault for not checking up on the market prices of the items you sold to him. You also accepted the prices he offered you by confirming the trade, and he did not promise anything you did not get. Sadly, there is not much you can do about it.

Any chance you know the scammers steam name?