Less remarked upon is a small cross-slab that once stood in the monks' graveyard there, and which has since disappeared entirely. When archaeologists A. O'Sullivan and J. Sheehan recorded it in 1996, it was a rough slab measuring just 33 centimetres high, 25 centimetres wide, and 3 centimetres thick, a fragment modest even by the understated standards of early Irish monastic stonework. Today, no visible remains of it survive.

Cross-slabs of this kind, flat stones incised or shaped to indicate a cross, are among the most common markers found in early medieval monastic cemeteries in Ireland. They were rarely elaborate; their purpose was functional and devotional rather than commemorative in the way later grave markers would become. On a site as exposed and wind-scoured as Skellig Michael, where the community of monks lived in stone beehive cells and endured some of the most severe Atlantic weather imaginable, even a small slab like this would have represented a deliberate act of marking, of claiming a particular patch of ground as sacred and remembered. That it has since vanished, whether lost to erosion, displacement, or simple deterioration of the stone, makes it a minor but telling example of how much even well-documented sites can quietly shed over time.