They knew this man.

They might have known about the cave.

They might have watched him leave and never return.

We have no evidence about them.

They have not been found.

This is the normal condition of early Holocene archaeology in most of North America.

The record is sparse, fragmentary, and highly dependent on accidents of preservation and discovery.

For every site that has been found and dated, there are dozens or hundreds of sites that were used and abandoned and then lost to erosion, agriculture, development, or simple failure of preservation.