Is Sujud As-Sahw (prostration of forgetfulness) obligatory for someone who missed the first rak'ah of Asr prayer and then, out of forgetfulness, said the taslim with the imam before performing the missed rak'ah?

If a ma'mum (follower) makes a mistake (commits sahw), he is not required to perform the prostration of forgetfulness (sujud al-sahw) unless he is a masbuq (one who joins the prayer late), because the Imam bears responsibility for his forgetfulness. The proof for this is the Prophet's (peace be upon him) saying: "Indeed, the Imam was appointed to be followed, so do not differ from him." However, if the ma'mum is a masbuq and commits sahw after his Imam has given the salutation, then he must perform the prostration of forgetfulness after completing his prayer, because he completes it individually.