As a general rule, Valve don't return scammed items. He can create a support ticket if he likes, because they do occasionally return items.

Please check Steam Trading Policy.

Originally posted by Champelliot:

because they do occasionally return items.

Don't worry, not going to be another one like this. But I would really like to know if that is true. Do you have any links to support that?

I've heard they sometimes give you back items you deleted/crafted accidentally but I've never heard of a case where they returned items from an unfair trade. All trades are final.

Once in a while I have heard a thing where Support has given a scammed hat back. Very, VERY rarely, though. It's always worth asking them but don't expect a yes.

I also got scammed out of my unusual hat 10 months ago, all that support agent said was "You have agreed to the trade twice by checking the box and pressing "Make Trade" button." They won't return any items back. A freind of mine, Atomic Potato, got his account hijacked once and all unusuals and other items he had were stolen. He contacted steam support 4 times asking to get his items back but they refused to do that. So, we're screwed now.