Por que Dumbledore nunca pensou em checar a Murta Que Geme? [duplicado]

Quanto mais vezes leio a série, mais me deparo com coisas que deveriam ter sido óbvias.

No livro Harry Potter e a Câmara Secreta, Harry supõe de repente que a garota que morreu no banheiro feminino 50 anos antes era de Murta Que Geme.

“Ron — that girl who died. Aragog said she was found in a
bathroom,” said Harry, ignoring Neville’s snuffling snores from the
corner. “What if she never left the bathroom? What if she’s still
there?”
Ron rubbed his eyes, frowning through the moonlight. And
then he understood, too.
“You don’t think — not Moaning Myrtle?” 

E eu tenho certeza que o diálogo dele entre Tom Riddle e Alvo Dumbledore descobre que Dumbledore quis dizer 'desde' a morte da garota.

“Well, hurry off to bed,” said Dumbledore, giving Riddle exactly
the kind of penetrating stare Harry knew so well. “Best not to
roam the corridors these days. Not since . . .”
He sighed heavily, bade Riddle good night, and strode off. 

E então, conforme o professor Binns,

Professor Binns looked faintly annoyed.
“The whole thing is arrant nonsense, of course,” he said. “Naturally,
the school has been searched for evidence of such a chamber,
many times, by the most learned witches and wizards. It does not
exist.” 

O Ministério da Magia poderia ter previsivelmente ignorado as pistas que levam injustamente à expulsão de Hagrid. Mas Dumbledore sempre achou que Hagrid era inocente. Nesse caso, eu me perguntei por que Dumbledore ou qualquer outro não percebeu essa ligação óbvia e questionou Myrtle como Harry fez.