O que aconteceu com o livro de fazer poções do Enigma do Príncipe depois que Harry o escondeu na Sala Precisa?

Você está certo em primeira instância, Harry não conseguiu recuperar o livro.

Todos são grandes e menores 7º spoilers de livros

And so it burned (as well everything in the room) when Crabbe casted Fiendfyre inside the room in The Deathly Hallows.

Como você pode ver aqui:

"I know what the diadem looks like, and I know where it is,” said Harry, talking fast. “He hid it exactly where I hid my old Potions book, where everyone’s been hiding stuff for centuries. He thought he was the only one to find it. Come on."

e depois:

There it was, right ahead, the blistered old cupboard in which he had hidden his old Potions book, and on top of it, the pockmarked stone warlock wearing a dusty old wig and what looked like an ancient, discolored tiara.

Harry deixa o livro na Sala de Requisitos, o destino final é que ele queime no livro 7 quando a sala queima (a menos que outro aluno desconhecido o encontre entre o final de 6 e o final de 7).

below them the cursed fire was consuming the contraband of generations of hunted students, the guilty outcomes of a thousand banned experiments, the secrets of the countless souls who had sought refuge in the room.