Somewhere beneath the streets of Waterford city, the remains of a medieval church dedicated to St Brigit may be lying undisturbed, its exact whereabouts genuinely unknown. Not lost to time in the romantic sense, but practically mislaid: the site is thought to lie somewhere around Catherine Street, but no excavation has yet confirmed it, and the building has left almost no trace above ground.

The church has a notable institutional history. In 1224 it was granted to the Knights Templar, the military religious order whose properties across Europe were seized following the order's suppression in the early fourteenth century. St Brigit's followed that familiar trajectory: by 1313 it had passed to the Knights Hospitaller, the order that absorbed much of the Templars' wealth and property after their dissolution. The church survived in some form for centuries after that transfer. By 1577 it was described as a hermitage, a term suggesting it had by then become a small, possibly solitary religious retreat rather than an active communal church, when it was granted to a man named George Moore. What happened to the structure after that point is not recorded.

Archaeological testing carried out in 2008 on a site at Bolton Street Yard, roughly fifty to a hundred metres east of where St Brigit's is presumed to have stood, offered an indirect glimpse of the area's buried past. Excavators found deep silts lying one and a half to nearly two metres below the present ground surface, with deposits of eighteenth and nineteenth century industrial rubble above them. The silts were shallowest towards the west, which led to the suggestion that an island, perhaps the ground on which the church once stood, may have lain in that direction. No physical evidence of the church itself was encountered. The city has, in effect, grown over and past it, leaving a documentary record without an archaeological one.