A book without a beginning

The Book of Mosiah is complicated.

In addition to numerous internally consistent references through the Book of Mosiah, there is another feature of the book that makes it unique--it is missing the beginning.

The original first and second chapters were part of the missing 116 manuscript pages.  Rather than re-translating this portion, Joseph Smith was instructed to start where he had left off.  As a result, we don't have many details about majorly important parts of the history of the Nephites, including:

• The daring escape of the Nephites from the land of their first inheritance and their journey through the wilderness to the Land of Zarahemla. (See Omni 1:12-13).
• The reign of King Benjamin's father, Mosiah 1--how he became king as a refugee to a foreign nation. (See Omni 1:19)
• The discovery of a lone Jaredite survivor, Coriantumr, and his short time with the Mulekites. (See Omni 1:21)
• Gazelem? (See Alma 37:23)
• 
  

Notice that in every other named book in the Book of Mormon, there is either a header that summarizes the contents of that book or (in the case of the shorter books) a first-person reference made by the author of the book.

Not so with Mosiah.  There is no header, and the first verse of "Chapter 1" begins:

1 And now there was no more contention in all the land of Zarahemla, among all the people who belonged to king Benjamin, so that king Benjamin had continual peace all the remainder of his days.

I find this aspect of the Book of Mormon to be curious to the point of incredulity. It forces me to ask a couple questions:

1. Who writes a book, develops all of these interesting story lines, and then leaves them out? 
2. If Joseph's motivation in writing the book was fame, why leave such a glaring gap in the text, which by so doing highlights the limits of his divine gift?

And yet, despite the glaring gap in the text, several internally consistent references point back at this missing section, including a reference to a place of resort near Shilom in Mosiah 11:13

...and he caused a great tower to be built on the hill north of the land Shilom, which had been a resort for the children of Nephi at the time they fled out of the land...