The monument appears on historical Ordnance Survey maps with shifting designations; marked as 'Standing Stone' on the 2nd edition six-inch map, it was later recorded as 'Gallan (site of)' on the 3rd edition, suggesting its disappearance occurred sometime between these surveys.

The stone's fate was documented by the antiquarian Kinahan in 1885-6, who noted that locals claimed it had been removed during construction of the Letterkenny reservoir. This would place its destruction during the late Victorian period, when Ireland was undergoing significant infrastructural development. The stone had occupied what was described as good agricultural land, which may have made its removal more palatable to landowners seeking to maximise their usable acreage.

Whilst no physical trace remains today, the site at Killyclug represents one of countless prehistoric monuments lost to Ireland's changing landscape. These standing stones, known locally as 'gallans', once dotted the countryside and likely served ceremonial, territorial or astronomical purposes for ancient communities. The careful documentation of such lost sites by the Archaeological Survey of County Donegal helps preserve at least the memory of these monuments, even when the stones themselves have long since been repurposed or destroyed.