I was planned to buy full Radioactive at the market, but I missclicked the item, I bought full gladiator and spent 5k.

The main problem is, the last time he's active was april 2014, his name is RyanPG. Can somebody please help me, especially Admins to bring back my TCs

you could file a scam report for an accidental trade
quoted from the scam reports rules and updates:
4) Accidental Trades

Originally Posted by Fee

Yeah, it happens to us all from time to time. We either send too much TC/items or send to the wrong username. It's inevitable even when you all practice the appropriate amount of care and attention (lol).

The scam board luckily does support these accidents, however below are a few guidelines you are required to follow:

• You are now required to firstly PM the user and explain the mistake. Running straight to the moderators isn't always the best idea, in most cases the user will be happy to return the items/TC.
• You are required to give the user at least 24 hours to respond to your PM and send the items back. Do not ask for the trade to be reversed before this time period has passed.
• You are required to provide proof of the original deal, we will NOT return items/TC unless we are 100% sure that they need to be returned. If the deal was made through the forums provide a link, if it was made through PM or in-game provide screenshots.

Your case will not be addressed until such time as all the above requirements are met. To help us help you effectively please fill in one of the forms listed below:

Wrong username
Items/TC accidentally sent:
Username sent to:
Username to be sent to:
Account History:
Evidence of deal:
Additional info:

Wrong items/TC
Items/TC sent:
Items/TC not intended to be sent:
Username sent to:
Account History:
Evidence of deal:
Additional info: