Well, he's not in your party then. If you appoint a companion a governor, they leave your party and are stationary in that settlement. You should be getting a monetary reward instead of the prize though as described in the patch notes:
- If the winner is the player character or a clan member who is in the main party, the tournament prize will appear in the player's inventory. Otherwise, the value of the prize in denars will be given to the winner's clan.