Being able to see living magical creatures was certainly fortunate, but Rhem cows had indeed gone extinct in North America.
Ilvermorny had preserved a great deal of information and, through blood research, artificially synthesized a substitute.
Blood, as a magical material, had many applications. Dumbledore had discovered twenty-one uses for dragon blood. Likewise, Rhem cow blood did more than enhance magical power; for a certain period of time, it could "restore youth."
The Philosopher's Stone did not "reverse time." Nicolas Flamel was still an old man; he had not turned into a young fellow.
Perhaps someone had treated the Philosopher's Stone as a wishing stone, believing it could become whatever they wanted.
When Bougainville left that island he had described as paradise, rich in black pearls, he had worried. He hoped nature would bless the islanders and keep them from catching Europe's greedy habits.
One local young man had asked to leave on the ship and go to France with Bougainville. Tahiti was not quite so untouched by worldly strife, after all. It fought with nearby islands, had privileged classes, and had ordinary people reduced to slaves or even sacrifices.
So the young man went with Bougainville. He followed at Bougainville's side for a time, then vanished into that country amid the tide of the French Revolution.
The "sorrow of disappearance" was not limited to animals. Astronomers were saddened by the "gap" between Ophiuchus and Scorpio as well, but that concerned distant galaxies, something humanity could not interfere with.
Georgiana had not told the French about that stone either. The magical fungus had formed because of the climate and soil there; if it were moved elsewhere, it would not form, regardless of whether it was moved for research or any other reason.
It was precisely because people feared the disappearance