"Faoiseamh" is the nominative form of the word ("faoisimh" is the genitive, which yo don't need in this construction); the past tense of "tarlaigh" is "tharla" (it's a bit irregular). I would probably say: "Thug sé faoiseamh dó nár tharla sé arís", or "Ba mhór an faoiseamh dó nár tharla sé arís", though I suppose you could also say "Bhí faoiseamh air nár tharla sé arís".