This doesn't make any sense. They were just lying on the surface where archaelogists just happened to be walking around? But if the find was legit, and the storm was responsible for the artifacts being churned up, how do they know where to dig? Or are they just gonna dig up all over the place?
The connection’s not very well made, but I think they just mean that the storm washed away some of the overburden and made it possible to see what was there. On the top of the hill, the artifacts couldn’t have washed in from somewhere else.