All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
You have to make up for that prayer because you ended it while being unsure whether you had performed the second Rak‘ah or not. Hence, you have failed to clear your liability in the best manner since one can only clear his liability with certainty (incontestable evidence and not mere doubts).
Therefore, you should not have performed the prayer until you had regained full consciousness so that you would be aware of what you are saying. Allaah The Exalted Says (what means): {O you who have believed, do not approach prayer while you are intoxicated until you know what you are saying …}[Quran 4:43]
Allaah Knows best.