Finding the Nephites in Ancient America

In 1997, a non-Mormon emailed me with questions concerning problems he saw with the Book of Mormon. He couldn't understand why the archaeological digs in Central and South America haven't found 'proof' of Mormonism.

I wrote him, responding that the possibility of a limited geography scope for the Book of Mormon is very high, given the variety of ancient nations (Mayan, Olmec, Aztec, Zapotec, Toltec, etc.) in Central America, not to mention South America. Many ruins are still hidden, and it is possible we may not have found the peoples of the Book of Mormon as of yet. And of the ruins found, many do not fit the time frame of the Book of Mormon (many date from after it), so can be definitely determined as other races or forgotten remnants of the Book of Mormon nations.

He replied stating that his archaeology professor called this rubbish, insisting that satellites are now used to find probable archaeological sites.  As this is very true, it doesn't cover a couple things:

Although recognized from the air, satellite images cannot determine the age of a ruin or what group may have used the site.
Without digging through an area, we cannot assume it belongs to one age or another, since many sites were built upon each other (sometimes by different nations which succeeded each other), some lasting for millenia.
For example, the great Mayan city of Tikal was built upon for 1500 years. During that time, at least 5 levels have been discovered. Considering that cities were built layer upon layer and foundation upon foundation, just finding the top layer of a city does not establish the entire story of a city.  

Secondly, many of these sites currently being excavated are the efforts of decades of digging. Tikal has been worked on by the University Museum of Pennsylvania for about 40 years. Thankfully, through their diligence, we have some wonderful discoveries from that place. Yet, they are far from finished, with thousands of earlier platforms and buildings still waiting excavation.

With such efforts being done in a single spot, how long will it take to uncover the hundreds of locations in mesoamerica? Especially considering most archaeological resources are given to digging up the Ancient Near East (Israel, Egypt, Jordan, etc.) or to local projects due to small budgets.

Given such odds, it is possible that the Book of Mormon nations may not have been encountered yet, or at least have been able to keep themselves in a low profile.  There are evidences being found in both Central and South America that show the Book of Mormon true.