So.. fake items?

Hello everyone.
So, just now is the third time I've lost some items, from a scammer.
I'm stupid, I know. But this time.. was 'different'..

I was trying to sell some skins in a trade server, when someone messaged me, asking to trade for them.
He offered a BS AWP Asiimov. Seemed legit.
I placed my items into the trade, and so did he.

Seemingly normal, I accepted the trade, and did the email. Everything in the email was legit too.
Upon accepting the email, my items went, and therefore I lost it.
I didn't receive the AWP, at all, even after DC'ing.

To this point, I'm still baffled as to how this happened.
I would love it if someone could explain how this happened // how to do it?
I'd not use it, except on those who used it against me.

I am very anti-scamming, and would like my items back.
I am not bothering with Steam Support, and yes, I know this is my fault.

If anyone knows anything at all, please tell me.
Either message me, or post here.
You can also Skype me:
jamie171000

Thanks.