Watch the full episode: https://www.youtube.com/watch?v=n1H_QlZ98yU
Travel across Canada and you are looking at thousands of square miles of glacial till, ground material pulverized by the weight and movement of the ice sheets, in some places hundreds of feet thick. When glaciers pass over a landscape, they do not preserve what was there before. They grind it.
The question of whether remnants of ancient structures could be buried in that till is not easily dismissed. If the buildings were constructed from clay or common rock, there is no obvious way to differentiate them from the surrounding material. The ice age did not just end a climate period. It reset the geological record across an entire continent.