Alexander Helios disappearance-Scriptural Nephites? According to Wikipedia, Alexander Helios is the son of Cleopatra VII. He disappeared fleeing Egypt with his people (roughly 50,000) after being defeated by Octavian in 31 BC.

His parents committed suicide after finding out about his disappearance. Alexander Helios was never found again. There are some theories that Egyptians came to America and left loads of treasure in the Grand Canyon.

They carved out a cave that looking as if it could hold 50,000 men. There is also a theory that they had built a pyramid inside the grand canyon somewhere on the North Rim. Here is a LINK to a News Paper Article of past findings. 

The Nephites in the Book of Mormon are considered very Egyptian and CAME to America. Is there a possibility that Alexander's group of people were the Book of Mormon Nephites?
No, the Nephites arrived in America around 600 B.C., long before Alexander Helios' days, with a much smaller group, on a single ship, and without their worldly treasures.

The Nephites are considered Jewish, not Egyptian, except for a remnant of their written language which was reformed from the Egyptian.