When Joseph Smith received possession of the plates again, after they had been taken back by the Angel Moroni in 1828 because of issues arising from the lost 116 pages that summer, Smith received a revelation concerning how to go forward with the translation process. In D&C 10:41 (emphasis added), the Lord instructed Joseph: "Therefore, you shall translate the engravings which are on the plates of Nephi, down even till you come to the reign of king Benjamin, or until you come to that which you have translated, which you have retained."
The few verses that comprise the text of Words of Mormon give us a bigger picture of the composition of the Book of Mormon. It is really quite remarkable that this, like so many other things, ends up being a very strong confirmation of the accuracy of the Book of Mormon, of its miraculous coming forth, and of the way in which the dictation occurred under difficult circumstances. It is hard enough for us to read the record and figure out what happened. Imagine Joseph Smith simply dictating these segments and putting them all together in the way that they all came through and making good sense. Although the details of how this precisely happened continues to be explored, discussed, and debated, it is textually clear that there actually were two records—the Words of Mormon and the book of Mosiah—that collided at this particular juncture and at the point where Harris lost the 1828 translation of the large plates down to and into the first part of the book of Mosiah.
Jack M. Lyon and Kent R. Minson, "When Pages Collide: Dissecting the Words of Mormon," BYU Studies Quarterly 51, no. 4 (2012): 120–136.
Brant A. Gardner, "When Hypotheses Collide: Responding to Lyon and Minson’s ‘When Pages Collide’," Interpreter: A Journal of Mormon Scripture 5 (2013): 105–119. As this topic continues to be discussed, see the comments between Gardner and Lyon as recently as November 26, 2019.
Royal Skousen, "Some Textual Changes for a Scholarly Study of the Book of Mormon," BYU Studies Quarterly 51, no. 4 (2012): 99–117.