We have huge canyons, valleys, and hills
Canyons : sites of erosion at tihs time, destroying (after exposing) the rocks and any fossils they contain. Hills similarly are sites of erosion. Valleys : sometime erosion, sometimes deposition as they transport sediment down-valley to temporary or less-temporary storage on their way to the sea. but definitely the valleys are the best chances for finding sites of deposition.
I guarantee with more ground penetrating radar or other scanning techniques there are other samples waiting to be found.
GPR - I've only used GPR down to about 40ft below sediment surface, and we couldn't get a good enough reading to be sure which structures were inclined bedding or void. not the easiest of things to interpret, as you'll know from your own work.
"Other scanning techniques?" Such as?
Still, being able to detect structure down to 40ft below surface doesn't give you permission to dig there, or the funding for the dig. Or the personnel. All the joys of trying to do science in a word of constrained funding and a population who, on average, don't give a flying fuck.