After a 100,000 or so odd years of chasing mega-fauna through the arctic circle it seems feasible that at least a few small bands of intrepid bipeds would of roved over the ice frontier into the North American continent.
These bands would have remained fairly small in the harsh new world and may have never established permanent settlements. Having to continually follow the herds they would have needed to traveled light, and left not much of a trace behind living upon the constantly shifting glacial ice...before being wiped out by the same event that extincted all the mega Fauna.