Go to Abu Bakr

Narrated Jubair bin Mutim (radi Allahu anhu): A woman came to the Prophet (sal Allahu alaihi wa sallam) who ordered her to return to him again. She said, “What if I came and did not find you?” as if she wanted to say, “If I found you dead?” The Prophet (sal Allahu alaihi wa sallam) said, “If you should not find me, go to Abu Bakr.” [The Book of the Virtues of the Companions of the Prophet: Sahih Bukhari]

This hadith is another indication by the Prophet (sal Allahu alaihi wa sallam) that the person most suitable to be his successor (khalifa) is Abu Bakr (radi Allahu anhu).