That uncertainty is not a gap in the record so much as the record itself. A cairn, typically a mound of stones raised over a prehistoric burial or used as a landscape marker, was identified at this location from an aerial photograph taken in April 1974. The image was convincing enough that the site was formally classified, first in 1992 and again in 1997, under the cautious designation of "cairn possible". Then someone went to look.

When the hillside was inspected on the ground in 2000, nothing was visible above the surface. No mound, no scatter of stones, no trace of whatever the aerial photograph had suggested was there. This kind of outcome is not unusual in upland archaeology. Features that read clearly from the air, where shadows fall at low angles and the geometry of disturbed ground becomes legible, can disappear entirely when you are standing among the rushes and rough grass. Peat growth, agricultural disturbance, or simply the angle of the light can account for the discrepancy. What the 1974 photograph caught may have been a genuine prehistoric structure, now reduced below the threshold of surface detection, or it may have been a trick of terrain and tone that mimicked one. The classification was never upgraded, and it was never removed either, sitting quietly in the official record as a possibility that the landscape declined to confirm or deny.