1. If the Lehites met "others" in the New World, why are they not mentioned?
2. What about those verses that imply that the Lehites were alone in the Americas?
Let's discuss the first question today.
When Nephi began recording their history from Jerusalem to the New World, it's possible he included details about encounters with native New World peoples. This would have been recorded on what is known as the "large plates" of Nephi (1 Nephi 9) which was later abridged by the prophet Mormon. Mormon -- who wrote his abridgement roughly 1,000 years later -- may or may not have felt it important to included details about "others" from a millennium earlier.