Terri's sleuthing may have found the kidnapped woman, but she put herself and other people in danger, and that is why McGarrett lectured her. I can't imagine him keeping quiet about it. If she had notified McGarrett of what she found, that would have been different, but the writers employed the pesky reporter taking matter into their own hands story line, and the end result was that she got a tongue-lashing from McGarrett, and deserved it.