I have believed all along we know so little of man's travels from the last glacial peroid because much of where man lived, is now under many feet of the ocean and sand/mud. If man came into the new world along the coast, many places where he would have come ashore are gone, washed away. Same in the Far East.
the bulk of the glaciation-era human habitat is still there, but submerged. The meltwaters issued forth catastrophically in at least a couple of places, but the rest of the continental shelf is merely covered by water. :')