Bem, sugiro que você leia o livro novamente. Porque Snape estava lá e o trio - Harry, Ron e Hermione o viram durante a reunião (na verdade, ele teve um vislumbre dele). Fred e George dizem a todos sobre Snape estar na reunião naquele dia
Fred heaved a deep sigh. “Shame. I really fancied finding out what old Snape’s been up to.”
“Snape?” said Harry quickly. “Is he here?”
“Yeah,” said George, carefully closing the door and sitting down on one of the beds; Fred and Ginny followed. “Giving a report. Top secret.”
“Git,” said Fred idly.
Uma vez que eles são convocados para o jantar, o trio realmente vê Snape sentado no centro da mesa:
“Yeah, yeah,” said Ron. “C’mon, I’m starving.”
He led the way out of the door and onto the landing, but before they could descend the stairs — “Hold it!” Ron breathed, flinging out an arm to stop Harry and Hermione walking any farther. “They’re still in the hall, we might be able to hear something —”
The three of them looked cautiously over the banisters. The gloomy hallway below was packed with witches and wizards, including all of Harry’s guard. They were whispering excitedly together. In the very center of the group Harry saw the dark, greasy-haired head and prominent nose of his least favorite teacher at Hogwarts, Professor Snape. Harry leaned farther over the banisters. He was very interested in what Snape was doing for the Order of the Phoenix.
Depois disso,
They heard the front door open and then close.
“Snape never eats here,” Ron told Harry quietly. “Thank God. C’mon.”
Então, Snape estava lá e ele também foi visto.