A bullaun is a boulder or slab bearing one or more deliberately carved cup-shaped hollows, and these stones are found at early medieval ecclesiastical and sacred sites across Ireland, where they were associated with ritual, healing, and in some cases cursing. The one at Threewells appears to have been quietly absorbed into the fabric of the place, built into a dividing wall at the holy well site rather than left freestanding, which is itself an unusual fate for such an object.

When the site was inspected in 1990, the stone was gone. No trace of it remained in the wall or elsewhere on the grounds. Whether it had been removed, broken up, buried, or simply lost to gradual dismantling of the wall structure is not recorded. The source material, published by Grogan and Kilfeather in 1997, notes its prior existence but offers no further account of what became of it. Its current location remains unknown.