Pilltoan House in Poulmaloe, County Wexford, found itself in exactly that position when it was included in the Sites and Monuments Record in 1987 under the mistaken belief that it might mark the location of the medieval castle of Alderton, also recorded as the castle of Ballyfarnoge. The structure on the ground, however, turned out to be a 19th-century farmhouse, built on the site of an earlier house, with no direct connection to the castle the compilers had hoped to pin down.

The castle of Alderton or Ballyfarnoge is a genuine historical site, recorded separately in the monuments inventory, but its precise location proved elusive enough that Pilltoan House was briefly considered a candidate. Once the farmhouse was properly assessed, the error was acknowledged and corrected. It is a small administrative footnote in the broader project of cataloguing Ireland's archaeological landscape, but it illustrates something worth knowing: the process of identifying and locating historic sites is genuinely difficult work, prone to reasonable errors, and the record is periodically revised as buildings are reassessed and older assumptions are tested against the evidence on the ground.