I did get a chance to look up Hartnett's book. Alas, he only includes his English translations; O Bruadair's originals aare not printed alongside. None of the poems in that small volume resembles the poem of Tomás an Buile. I haven't been able to look at the larger volumes nor at James Stephen's "Collected Poems". I wouldn't expect the latter to include the Irish language original, but it might credit the original author and/or give the century the Irish -language poem was written. On the other hand, the Stephens book might just say "translated from the Irish"! I still haven't remembered or figured out why I thought it was a translation from O Bruadair.