Sahih Bukhari Volume 009, Book 089, Hadith Number 327.
Narrated By Jubair bin Mut'im : A woman came to the Prophet and spoke to him about something and he told her to return to him. She said, "O Allah's Apostle! If I come and do not find you?" (As if she meant, "...if you die?") The Prophet said, "If you should not find me, then go to Abu Bakr."