Well, I see you already gave him the negative rep and wrote down why.
You can report him to SteamRep: https://steamrep.com/
and can "Report a a Violation: Attempted Trade Scam" on Steam...by going to his profile, left clicking under the "More" Tag located under his nickname. You should provide your evidence to both of those sites.
Also, when about to trade, pick a person with more rep as you are starting out, check them out on Steam (Look for account older than 2 years, >100 games, Level 10 and above, good amount of unbanned friends, Active playtime, etc.), SteamRep and TF2 Trader if possible.
While, at a quick glance, I don't see any suspicious features in his Steam account...his SteamTrades account certainly has low rep and had some negative feedback even prior to your trade.
Nothing will make you foolproof to scams if you trade regularly, but look up the other person to make sure they are legit and if you do it right your risk of falling for a scam is really low, the goal is to keep it that way. :)
Also beware phishing scams.
Hello. :)
I attempted to add you for this trade you posted here:
Sorry I didn't respond right away after you accepted my friend request and messaged me. Not sure if you blocked me now or not, but feel free to add me if you're interested in that trade still. :)
Hey there! Nah, you're not blocked. Didnt get a response hence the removal. Sorry about that, I usually only keep friends I know on my list.
Thanks for the response though. Unfortunately, I've traded that game awhile back.
Scammer profile
Steam ID
We agreed to trade Valiant Hearts for Universe Sandbox. I offered to go first as I am new to this. After receiving my game, he went offline and proceeded to block me without keeping to his side of the deal.
Proof
Doesn't feel good to be scammed so early in my trading experience but I guess its the price for learning.
I contacted someone on his friend list who is an amazing person! He helped me ask the scammer why he did it. My heart fell when I read his response and to find out there are people like this out there.
Chat with amazing guy
Now, my question is...how do I report him to Steamtrades? Can he be banned for this? I would not want another person to be his victim.