What? The hacker has his armor, if the hacker is banned, whatever he had in his inventory is therefore taken with him and no longer in the game. He can no longer receive the Winter set from the hacker and needs a refund.
Since you're not really getting a straight answer and there's post-farmers on here, I'll give you a to-the-point response:
If you have proof of being in possession of Winter Gear and that it was taken from a hacker, you can easily make a Troubleshooting thread or PM an admin with the proof. If you don't have the proof, you're out of luck. It should be reasonable for you to get your items back if you were telling the truth.