St Mogue's Well survives, sitting roughly 150 metres to the north-east of the old church in the area, and it retains enough of a presence to be located and identified. But beside it, or very near it, a second well was once said to exist, and that one has proved considerably more elusive.

John O'Donovan, the nineteenth-century scholar who travelled Ireland in the 1830s compiling place-name and antiquarian records for the Ordnance Survey, noted that a well called St Caillin's Well lay within a few perches of St Mogue's. A perch is an old unit of measurement, roughly five metres, so the two wells would have been almost neighbours. The name Caillin connects the site to St Caillin of Fenagh, a figure associated with early Christian monasticism in Leitrim. That connection is reinforced by a seventeenth-century list of holy places in north Leitrim, which includes a Tobar Callain at Rossinver, suggesting the well had some recognised significance in the region for centuries. Holy wells in Ireland were typically focal points for patterns, local devotional gatherings held on a saint's feast day, often involving circumambulation of the well and the tying of votive offerings to nearby trees or bushes. Whatever rituals may once have been observed at St Caillin's Well, the site itself has since disappeared. No physical trace has been identified, and the well is no longer known locally, meaning the oral tradition that might have kept its location alive has also been lost.