Workers uncovering sand at Sonna Demesne came across what appeared to be human remains. Several unprotected burials were found and, remarkably, reburied elsewhere before anyone considered alerting the authorities. It was only the presence of a stone-lined grave that gave the workmen pause; they covered the remains and waited, though in the interim some of the bone was carelessly thrown back in on top of the burial. The National Museum of Ireland was not notified until 10 August.

Archaeologist Breandán Ó Ríordáín arrived and conducted a two-day excavation, uncovering three distinct burials. The first and third were slab-lined and unprotected inhumations respectively, both dated by radiocarbon analysis to the early medieval period. The second, which Ó Ríordáín found immediately east of the first grave at a depth of nearly a metre, was something older altogether. It was a short cist, a small stone box burial of the kind used during the Bronze Age, constructed from edge-set slabs leaning inward and sealed with a single capstone roughly 78 centimetres long. Inside, beneath a layer of sand, lay the cremated bones of an adult male alongside a ceramic bowl. The bowl, a tripartite form associated with stage 3 of the Bronze Age bowl-making tradition, was already broken when found, possibly damaged when one of the cist walls shifted over the centuries. Radiocarbon dating of the cremated bone calibrates to between approximately 2135 and 1746 BC, placing this individual in the early Bronze Age, more than a millennium before the people buried in the graves closest to him. The human remains were examined by Dr David M. Davies and later re-examined by Laureen Buckley, while Cahill and Sikora published a detailed account of the site in 2011.

What makes the site quietly unsettling is not any single burial but the accidental layering of time it revealed. Early Bronze Age cremation, early medieval inhumation, and an unknown number of other burials disturbed and scattered before any archaeologist arrived: all of it tucked into a working sandpit on a mild incline above the Westmeath countryside, noticed almost by chance, and very nearly lost entirely.