What makes it stranger still is that it was never truly visible until the twentieth century, when an engineering project accidentally brought it to light. The site is a lithic scatter, meaning a concentration of worked stone left behind by prehistoric people, in this case fragments of chert, a flint-like rock that Mesolithic toolmakers knapped and shaped, leaving behind the small waste flakes known as debitage.

The exposure of this material came about through drainage works carried out on the Inny River in the 1960s, which lowered the water level of Lough Derravaragh and uncovered what had been the Mesolithic shoreline of the lake, submerged for thousands of years. Professor Frank Mitchell recorded the find in 1972, designating it Site 3 in his survey of the area. He described a bay cut into the south end of a raised bog, where an irregular surface of eroded fen-peat held a small scatter of chert debitage and stone. Raised bog and fen-peat are both forms of wetland accumulation, and it is precisely these waterlogged, oxygen-poor conditions that can preserve organic and lithic material over vast stretches of time. The shoreline that emerged from beneath the water had effectively been sealed since the Mesolithic period, roughly the middle Stone Age, somewhere between nine and four thousand years before the present. No surface remains of the scatter are visible today.