I've searched a bit on HlStats and I've found a player with the same name but the date doesn't really match, this guys last session online was on November 28th with the
Steamid: STEAM_0:1:28907187
But we can't ban the person unless we're 100% sure it's the right one. Did you maybe get the dates confused?
I will try to dig deeper into this and see if I can find a match.
Regards,
Melisa