Was this fair punishment for my 11 year old daughter?

My 11 year old is in her school's chorus. She was in the room the chorus practices in before a concert last night and the chorus teacher was busy with something else. She found some sheet music that she knew was the song they were learning next for their Christmas concert, and picked one up out of curiousity. The chorus teacher saw her, and she put it back and apologized. But that wasn't enough, apparently. The chorus teacher freaked out and yelled at her telling her how wrong it was of her and yelled at her for what my faughter described was "forever". Was this really fair? My daughter was just curious, I don't think she deserved that! Also, the chorus teacher knew it was the sheet music and not anything personal of hers, my daughter made that clear.