Well, what Elfwyn said. I also very curious why a Ravenclaw like Harry has to walk through the door. Just blast the wall off or fly over it or somethings. He's blast through Askaban's defend while he was 6 for god's sake!
And doesn't he even know of the existent of the Horkrak? He has nearly 10 years searching for it. Doesn't look like he do any research at all.