Invalid TF2 Scammer please help!

JoshMcPwnage (the scammer's name) scammed me out of a strange shotgun!
Please help now he is saying that its his and doesn't want to give it back :'( i
I am really sad that i don't have it so please help me please!
I don't have any proof because i didn't know he would scam me but please help!
I would be very happy if i at least got my shotgun back!

Invalid report format
Please adhere to the guidelines below when submitting a report:
http://forums.steamrep.com/threads/...-look-at-acceptable-format-before-posting.51/

In addition, please provide evidences like screenshots of the trade inventory history and steam chat conversation as well.

Here's how you do it:
http://forums.steamrep.com/threads/howto-provide-evidence-with-screenshots.3488/

Going to put this as invalid.