How did the Prophet pray before the five daily prayers were made obligatory, and what should one do after forgetting a bowing in prayer?

Summary

According to the view of al-Harbi cited in this fatwa, the prayer of Muslims before the Isra and Mi'raj consisted of two rak'ahs in the morning and two rak'ahs in the evening, consistent with al-Hassan's interpretation of the verse on glorifying God in the evening and morning. For someone who recalls during the final tashahhud that the bowing of the second rak'ah was missed, mere doubt is disregarded and the prayer is completed as usual. If the omission is certain, one additional rak'ah must be added to complete the prayer.

Written in our own words from the original fatwa — check the source before acting on it.