The ruling on one who forgets the second prostration of the final rak'ah

Question:
An imam prayed the 'Asr prayer, and during the final rak'ah he prostrated only once, then sat for the final tashahhud and said the taslim. After that, one of the worshippers alerted him that he had prostrated only once and had not prostrated the second time except in the final rak'ah. Then he stood up and prayed a complete rak'ah with them, sat for the tashahhud, then said the taslim, and performed sujud al-sahw. Is this manner correct?

Answer:
Yes, this is what is prescribed. If one leaves out a prostration and says the taslim, then remembers or is alerted, he stands up and performs a rak'ah, then completes the prayer, then says the taslim, then performs one prostration for forgetfulness after the taslim, which is better.

Question: And if he prostrates before the taslim?

Answer: It suffices, it suffices, but the better option is after the taslim, if he said the taslim due to a deficiency.

Question: And if the prostration is performed...?

Answer: No, it does not suffice, yes; because he has already said the taslim.

Question: But Shaykh, he did not have a deficiency, meaning we say: he is now praying the Zuhr prayer, sat in the third rak'ah, and they told him: Subhan Allah. Does he say the taslim after the...?

Answer: No, if they said: Subhan Allah, and he stood up; his prostration is before the taslim. This case is only when he said the taslim, then they alerted him.