Itinerant hunter-gatherers.

Half a mile from where I live, on Heysham Head, a long-suspected mesolithic site was excavated in the '70s. The evidence was strongly in favour of it being a permanent site. There was much evidence of reindeer and elk (actually bones are occasionally still uncovered by the sand) and many flint and bone tools were uncovered. The nearest source of workable flint is over 150k distant, and some of the arrowheads were originally worked in France. Although our guys moved in and settled as the ice receded 9000-10000BC, they were obviously pretty mobile. The site was only abandoned when agriculture took over, mostly because the land wasn't very fertile.
Potsherds are organic, and will not survive thousands of years in an acid soil. None at all were found at Heysham.