The more we learn about Mesoamerica, the less we need a separate record. If the Spanish hadn't destroyed so many of their records, we may have known as much about the Mayans as we know about any culture of an equivalent time period.
(I'm going to pass over the point that it was the Spanish, not the Lamanites, who destroyed their records.)
But the Book of Mormon was preserved to tell a particular people--descendants of Lehi, primarily--about their history and covenants. Does this make sense if those descendants kept meticulous and detailed records for centuries, like the Mayans did? If those descendants wrote their history on their buildings in stone to be preserved for hundreds of years?
If we're looking for the descendants of Lehi, we should be looking for a people who had forgotten their history, who didn't know the origins of the archaeological ruins they lived among, who had no written records... A people who could only learn about their history through a record hidden away so it wouldn't be destroyed, and then brought forth in the future.
We have that record: it's the Book of Mormon.
Now, for whom was it written? For the Mayans, who had many records going back hundreds of years (although the Catholic Priests and monks burned most of the codices, they still had stone monuments and stelae)?
Or the North American Indians, who had lost all knowledge of their ancestors apart from a few oral traditions?
The Mesoamericanists don't recognize the irony that the more they learn about Mesoamerica, the more they prove there was no need for ancient prophets to seal up a record to restore a lost history from that area.