If the imam prostrates for forgetfulness after the closing salam and the one who joined the prayer late has already stood up, does he go back to prostrate with the imam?

Question:
He says: Honorable Shaykh, may Allah grant you success. If the imam says the salam to end the prayer and then prostrates for forgetfulness after the salam, and the one who joined the prayer late has already stood up, does he go back to follow the imam in his prostration for forgetfulness?

Answer:
If he has already settled into standing, he does not go back. But if the imam prostrated before he had settled into standing, it is obligatory for him to go back. Yes.