Does the prostration of forgetfulness (sujud sahwi) become necessary for someone who said "Rabbana wa lakal hamd" (Our Lord, to You be all praise) before "Sami‘a Allahu liman hamidah" (Allah hears the one who praises Him), and then remembered at that very moment?

"Sami'a Allahu liman hamidah" (Allah hears the one who praises Him) is said while rising from bowing (ruku'). "Rabbana wa lakal-hamd" (Our Lord, and to You be all praise) is said after rising from bowing, by both the Imam and the one praying alone. As for the congregant (ma'mum), he only says "Rabbana wa lakal-hamd" when rising from bowing. If someone says "Rabbana wa lakal-hamd" during the act of rising, they should also say it after rising because it was said out of its proper place. This verbal addition does not invalidate the prayer, and there is a difference of opinion regarding the permissibility of performing the prostration of forgetfulness (sujud as-sahw) for it.