Steam will no longer give you back items lost in a trade scam 

Valve has changed its policy pertaining to items lost in trade scams.

Going forward, Valve is longer going to reimburse users who were victims of item trade scams. The FAQ has been updated to reflects this change saying, "We sympathize with people who fall victim to scams, but we provide enough information on our website and within our trading system to help users make good trading decisions. All trade scams can be avoided."

According to Valve, giving users back their lost items had an effect on these items' market value, which is one of the reasons for the policy change.

"Our community assigns an item a value that is at least partially determined by that item's scarcity. If more copies of the item are added to the economy through inventory rollbacks, the value of every other instance of that item would be reduced," said Valve.

The full set of questions and answers deals with the most common cases of fraud and scam, so make sure you read it if you do trading on Steam.