Pope Benedict XIV pointed out (1) that we are obliged to venerate an exposed Host (cultum negari non posse hostiae ad venerationem expositae). But (2): although it is de fide that consecrated Hosts have been transubstantiated, (3) it is not de fide that this particular host actually was, as a matter of History, certainly consecrated (licet de fide non sit esse consecratam).
You see what he means in part (3) of that. The validity of its (or Its) consecration depends on our certainty that Fr O'Flanahan did say the proper words over it with an adequate intention (poor old chap undoubtedly getting senile) and that the novice nun who baked it did get the recipe right (last week her scones tasted of Vindaloo) and that the village miller's labourer didn't confuse his wheat-grain with his barley-grain (should have gone to Specsavers) and that our rather cranky Sacristan Maire Murphy didn't surreptitiously substitute an unconsecrated host for the consecrated Host (has brainstorms every alternate full moon) and that the priest who baptised Fr O'Flanahan, the notorious Fr Jack Hegarty of Graggy Island, didn't deliberately do it invalidly (by withdrawing his intention to perform any sort of Christian rite) in order to take revenge on bishop Brennan for cutting off his supply of whiskey and girls.
[Can I just break off here to clarify that I am not anti-Irish ... if the officiating clergyman had been, not Fr O'Flanahan of the County Tipperary but Fr Featherstonehaugh-Cholmondeleigh, Eton, Kings, and the Beda, one of the Barsetshire Featherstonehaugh-Cholmondeleighs (note for transatlantic readers: pronounced 'Fanshaw-Chumly'), I could have gone on for pages and pages more ... ]
While we are in via, even the majesty of Dogma does not free us from dependance on ordinary human probabilities. Watertight logical certainties guaranteed by a string of immaculate syllogisms are not the stuff of our Christian lives.
The other day, Bishop Robert Barron lectured memorably in the University Church on S John Henry's Grammar of Assent. I wonder if the Lambertini Conundrum gives interesting Magisterial support to the argument of the Grammar!