What is the ruling if a traveler intends Qasr, but the Imam invalidates his prayer before the follower is aware of the Imam's true status?

Primary text

If the follower intends to shorten the prayer, and then his Imam invalidates his state of prayer before the follower becomes aware of the Imam's actual status, the follower is permitted to shorten the prayer because the outward appearance indicated the Imam was a traveler, due to the existence of its evidence. The intention to shorten was permitted based on this apparent situation.