Fascinating details below and found here.
New research strongly demonstrates that Joseph Smith started the translation of our current Book of Mormon with the Book of Mosiah. This is because when the 116 pages were lost, Joseph Smith simply started translating from where he left off, in Mosiah.
This provides strong evidence for the truth of the Book of Mormon, because there are hundreds of references in the Book of Mormon to earlier content (content that Joseph Smith hadn’t even written yet). So either Joseph Smith was the most talented author of all time, or he was simply translating an ancient record. Watch here!
Additional evidence of a Mosiah-first translation: When Pages Collide: Dissecting the Words of Mormon
Careful readers of the Book of Mormon have probably found verses 12–18 of the Words of Mormon to be a bit of a puzzle. For stylistic and other reasons, they do not really fit with verses 1–11, so commentators have tried to explain their presence as a sort of “bridge” or “transition” that Mormon wrote to connect the record of the small plates with his abridgment from the large plates.
This paper proposes a different explanation: Rather than being a bridge into the book of Mosiah, these verses were originally part of the book of Mosiah and should be included with it.
This article presents both documentary and textual evidence to show that (1) Joseph Smith had translated some text that he did not give to Martin Harris (the lost 116 pages), (2) Oliver Cowdery, Joseph’s scribe, copied from the original manuscript onto the printer’s manuscript at the beginning of the book of Mosiah the chapter designation “Chapter III,” (3) verses 12–18 of Words of Mormon do not use the first-person pronoun “I” and do not speak of the small plates, as verses 1–11 do, and (4) the book of Mosiah begins abruptly, without an introductory heading and without any mention of the person for whom the book was likely named (Benjamin’s father, Mosiah).
These and other pieces of evidence support the idea that the last seven verse in Words of Mormon were actually the last verses of what should have been Mosiah chapter 2, but chapter 1 and most of chapter 2 must have been part of the 116 pages lost by Martin Harris.