A bullaun stone, which is a large boulder or rock with one or more deliberately carved cup-shaped depressions, typically associated with early Christian sites and sometimes with folk healing or cursing traditions, was reportedly found at Killeen in County Mayo, set within an enclosure and a children's burial ground. The combination alone is striking: bullaun stones turn up frequently near early ecclesiastical sites, and children's burial grounds, known in Irish as cillíní, were liminal spaces used for the interment of unbaptised infants, existing at the edge of consecrated ground and of official religious practice.

The local knowledge of the stone's existence was passed on by Francis McCann in 1991, and it was recorded accordingly. When the site was physically inspected in 1997, however, the stone was nowhere to be found within the enclosure. Whether it had been moved, buried, or simply obscured is not known. Its absence is now, in a way, part of the record itself, a gap that sits alongside the enclosure and the burial ground as a piece of the site's history.