Sometime between the first Ordnance Survey mapping of the area in 1841 to 1842 and the production of a later edition, the circular earthwork recorded there vanished from the landscape entirely, leaving no surface trace whatsoever. It is the kind of absence that raises more questions than a ruin would.

Ringforts, known in Irish as raths, were typically enclosed farmsteads of the early medieval period, defined by one or more circular earthen banks and ditches. Thousands survive across Ireland in varying states of preservation, but many others have been lost to centuries of agricultural clearance, land improvement schemes, and gradual erosion. The Ballyhorgan example was captured at precisely the moment when Ordnance Survey teams were making their first systematic record of the Irish countryside, a process that documented countless features, some of which were already on the cusp of disappearance. By the time surveyors returned to revise the maps, this one was gone. Whether it was levelled deliberately or simply worn away in the intervening decades is not recorded.