Is it sufficient to perform only the prostration of forgetfulness (sujud al-sahw), or is it obligatory to pray a full rak'ah along with the prostration of forgetfulness for someone who forgot the final tashahhud after the second rak'ah and stood up to recite Al-Fatiha?

If you miss two rak'ahs of Maghrib prayer, you stand up after the Imam's salutation and perform one rak'ah with Fatiha and a surah aloud, then recite the Tashahhud. Then, you perform another rak'ah with Fatiha only silently. If you forget the first Tashahhud after separating from the Imam, you are required to perform the prostration of forgetfulness (sujud al-sahw) before the taslim.