Should one repeat the prayer or perform the prostration of forgetfulness if one remembers its obligation fifteen minutes after the salutation?

If a worshipper forgets the prostration of forgetfulness (sujud al-sahw) and remembers it after a long time has passed, some scholars hold that their prayer is invalidated, while others maintain that it is not. Some differentiate between the pre-salutation prostration (qabli) and the post-salutation prostration (ba'di). Ibn Qudamah is of the view that the prayer is not invalidated by a long separation, and this is also the opinion of Al-Shafi'i and the jurists of opinion (Ahl al-Ra'y). Scholars have differed on the definition of "long separation"; some consider exiting the mosque to be a long separation, while others refer it to common custom ('urf). Al-Qadi is of the view that returning to the mosque after having exited it is permissible, and this is also the opinion of Al-Shafi'i. It has also been narrated from Ahmad that prostration is permissible even if the worshipper has left and gone far away. In conclusion, it is more prudent (ahwat) to perform the prostration of forgetfulness and repeat the prayer.