Where the 1838 six-inch map had simply recorded the word "Carn", the resurvey added two deflating words in front of it: "Site of". Something had been here, and now, for practical purposes, it was gone.

A cairn, in this context, is a prehistoric mound of heaped stone, often raised over a burial and sometimes marking a prominent point in the landscape. This one sat on a north-facing slope of craggy outcropping rock, just south of a bend in the road. The likely culprits for its disappearance are not mysterious. Stone is useful, and when a house was built to the east of the cairn, the mound would have offered a convenient quarry. The road itself probably caused further disruption. When the site was inspected in May 1982, vegetation had overtaken it, and only a possible arc of material remained visible on the western side, measuring roughly four metres long, two metres wide, and half a metre high. Even that was ambiguous, and investigators at the time could not say with certainty whether it was structural or simply natural rock formation. By a follow-up visit in November 1983, no surface traces were visible at all. A second cairn lies approximately sixty-five metres to the south-west, suggesting this was once a more substantial prehistoric presence in the landscape around Letterfrack than the current roadside gives any reason to suspect.