Is the prayer valid if the worshiper doubts having said "Rabbana wa Lakal Hamd" (Our Lord, to You be all praise) after rising from bowing?

According to the Hanbalis, the utterances of "Sami'a Allahu liman hamidah" (Allah hears those who praise Him) and "Rabbana wa lakal-hamd" (Our Lord, to You belongs all praise) upon rising from rukūʿ (bowing) are obligatory, and this is the correct view. If the worshipper doubts whether they have said them while still in the position for these remembrances, they should say them. If they doubt after having moved past that position, they must perform sujūd as-sahw (prostration of forgetfulness). However, this is waived if they join the imam in the first rakʿah. Otherwise, they should perform sujūd as-sahw before the taslīm (salutation). If they omit sujūd as-sahw due to ignorance of its obligation, their prayer is still valid.