Praise be to Allah.
Naafil acts which are done for a specific reason should not be made up once the reason is no longer present. For example, if the sun is eclipsed and a person was asleep, then when he wakes up he finds out that there has been an eclipse, he should not do the eclipse prayer because the occasion has passed. Similarly, if a man enters the mosque and stays there for a long time thinking that he does not have wudoo’, then he remembers that he does have wudoo’, he should not pray Tahiyyat al-Masjid (two rak’ahs to “greet the mosque” upon entering) because it is a Sunnah and the occasion for it has passed. The guideline in these cases is that every naafil act which is done for a reason should not be made up later, such as Witr. The Prophet (peace and blessings of Allaah be upon him) did not make up Witr as such; he would pray twelve rak’ahs of Duhaa (optional mid-morning prayer). The most he ever prayed in Witr was eleven rak’ahs, so he made up the most but he made it even, because the occasion for praying Witr had passed.