Anubhav comments on Harry Potter and the Methods of Rationality discussion thread, part 12

[Anubhav]

Miss Granger would remember the Imperius. Obliviation cannot be detected by any known means, but only a Professor could have cast that spell upon a student without alarm from the Hogwarts wards

‘She was Imperiused and then Obliviated’ seems to be the likeliest hypothesis.