the idea was that voldemort wanted to keep his return a secret
harry dying in the maze is believable, disappearing in hogwarts less so
But... that's exactly what happened. He
did
disappear in Hogwarts.
...while in the deadly maze.
River Song: Well, I was off to this gay gypsy bar mitzvah for the disabled when I thought 'Gosh, the Third Reich's a bit rubbish, I think i'll kill the Fuhrer'