É possível que o Hagrid escorregue quando fala com eles.

Sabemos que o Hagrid entra na Floresta Proibida e às vezes fala com os centauros. Também sabemos que o Hagrid teve dificuldade em manter em segredo informações sobre a Pedra Filosofal.

“Oh, a fair few … Keep themselves to themselves mostly, but they’re good enough about turnin’ up if ever I want a word. They’re deep, mind, centaurs … they know things … jus’ don’ let on much.”
_{^{- Harry Potter and the Philosopher's Stone, Chapter 15 (The Forbidden Forest)}}

Parece possível que o Hagrid poderia ter dito a eles que a Pedra Filosofal estava em Hogwarts. Ele acidentalmente deu a Harry informações suficientes para descobrir, e Harry era um garoto inexperiente de onze anos que acabara de aprender sobre o mundo mágico.

Parece improvável que eles tenham adivinhado - a adivinhação do centauro é ampla.

Embora seja possível que os centauros tenham adivinhado que a Pedra Filosofal está em Hogwarts, pelo que sabemos da adivinhação dos centauros, ela tende a ser mais ampla e não focada nos detalhes.

“Sybill Trelawney may have Seen, I do not know,’ continued Firenze, and Harry heard the swishing of his tail again as he walked up and down before them, ‘but she wastes her time, in the main, on the self-flattering nonsense humans call fortune-telling. I, however, am here to explain the wisdom of centaurs, which is impersonal and impartial. We watch the skies for the great tides of evil or change that are sometimes marked there. It may take ten years to be sure of what we are seeing.”
_{^{- Harry Potter and the Order of the Phoenix, Chapter 27 (The Centaur and the Sneak)}}

A partir disso, parece que eles não obteriam esse nível de detalhes das estrelas. Também parece que adivinhar coisas pode levar tempo, então eles provavelmente não descobririam o que está acontecendo. Quando ouvimos uma das previsões de Firenze, ela é muito ampla e não fornece detalhes específicos sobre nada.

“In the past decade, the indications have been that wizardkind is living through nothing more than a brief calm between two wars. Mars, bringer of battle, shines brightly above us, suggesting that the fight must soon break out again. How soon, centaurs may attempt to divine by the burning of certain herbs and leaves, by the observation of fume and flame …”
_{^{- Harry Potter and the Order of the Phoenix, Chapter 27 (The Centaur and the Sneak)}}

Ron descreveu a lição como nada muito definitivo e com poucos detalhes.

“He’s not very definite on anything, is he?’ said Ron in a low voice, as they put out their mallowsweet fire. ‘I mean, I could do with a few more details about this war we’re about to have, couldn’t you?”
_{^{- Harry Potter and the Order of the Phoenix, Chapter 27 (The Centaur and the Sneak)}}

Parece que eles não conseguiriam adivinhar a presença da Pedra Filosofal.

O que Firenze diz em Harry Potter e a Ordem da Fênix indica que os centauros, na maioria das vezes, conseguem apenas uma ampla variedade de coisas:

‘I know that you have learned the names of the planets and their moons in Astronomy,' said Firenze’s calm voice, ‘and that you have mapped the stars' progress through the heavens. Centaurs have unravelled the mysteries of these movements over centuries. Our findings teach us that the future may be glimpsed in the sky above us –'

‘Professor Trelawney did astrology with us!' said Parvati excitedly, raising her hand in front of her so that it stuck up in the air as she lay on her back. ‘Mars causes accidents and burns and things like that, and when it makes an angle to Saturn, like now –' she drew a right-angle in the air above her ‘– that means people need to be extra careful when handling hot things –'

‘That,' said Firenze calmly, ‘is human nonsense.'

Parvati’s hand fell limply to her side.

‘Trivial hurts, tiny human accidents,' said Firenze, as his hooves thudded over the mossy floor. ‘These are of no more significance than the scurryings of ants to the wide universe, and are unaffected by planetary movements.'

‘Professor Trelawney –' began Parvati, in a hurt and indignant voice.

‘– is a human,' said Firenze simply. ‘And is therefore blinkered and fettered by the limitations of your kind.'

Harry turned his head very slightly to look at Parvati. She looked very offended, as did several of the people surrounding her.

‘Sybill Trelawney may have Seen, I do not know,' continued Firenze, and Harry heard the swishing of his tail again as he walked up and down before them, ‘but she wastes her time, in the main, on the self-flattering nonsense humans call fortune-telling. I, however, am here to explain the wisdom of centaurs, which is impersonal and impartial. We watch the skies for the great tides of evil or change that are sometimes marked there. It may take ten years to be sure of what we are seeing.'

Firenze pointed to the red star directly above Harry.

‘In the past decade, the indications have been that wizardkind is living through nothing more than a brief calm between two wars. Mars, bringer of battle, shines brightly above us, suggesting that the fight must soon break out again. How soon, centaurs may attempt to divine by the burning of certain herbs and leaves, by the observation of fume and flame.'

Portanto, parece inteiramente plausível que os centauros possam ter aprendido sobre o esconderijo da Pedra Filosofal da magia da adivinhação.