At the end of the book of Alma, we saw that Mormon may have manipulated the division between the books to make that division line up on the culturally significant forty years of the reign of the judges. The beginning of the book of 3 Nephi may also have been slightly manipulated. In this case, the year of the reign of the judges is not necessarily significant, but the fact that “it was six hundred years from the time that Lehi left Jerusalem” was monumentally significant. In the very first verse, Mormon expects that his readers understand that there is a major prophecy to be fulfilled. The Messiah was to come six hundred years from the time Lehi left Jerusalem, and this book begins with that very year of that fulfillment.
When the book of Helaman ended, Nephi, the son of Helaman, was the prophet. In verses 2 and 3 we say goodbye to him, even though we do not know in exactly which year the transition took place. What we learn is that Nephi left. His death is not recorded, only his departure, “and whither he went, no man knoweth.” That is very much the way Alma the Younger’s death was recorded in Alma 45:18–19, where Alma simply went away and was not heard from or about again.