So...if a player attempts to trigger Burdensome Official (After you win a challenge in which Burdensome Official participated, attach Burdensome Official to an opponent's character. Kneel that character. That character cannot stand while Burdensome Official is attached.) and the effect is canceled, what happens to the character?
By character i meant the Burdensome Official.
The effect changes it from one state (character) to another (attachment). If the effect is canceled (and since there was nothing trying to remove it from play as part of the cost), the Burdensome Official remains as it was when the effect was triggered.