Unfortunately, if you are unable to find the SteamID of the user who you believe to have scammed you, then we have no way to prove who it was, and it would be difficult even for a CM to find it through checking the logs, since there would probably be others with the same / a similar name.
Without a SteamID and proof of that SteamID, then there is nothing we can do I'm afraid. Remember you can type "status" into console or click on a user's name in the TAB menu in order to easily find their SteamID and proof of it.