Wood decided to keep Harry's participation in the Quidditch match strictly confidential, treating him as a secret weapon for the Gryffindor team to catch their opponents off guard during the game.
Yes, a secret weapon—yet secrets always have a way of spreading.
The very next day after Harry became the Gryffindor Seeker, the entire school knew the news that Harry was going to play as Seeker.
Chapter 308