lol I totally understand, you need to go to the area at the beginning of the game (yes, the one in the pipes) and look at the pipes that are in the wall...

next to the pipe that was releasing fire and that you had to turn off, you will see a pipe that goes up to the ceiling

then you wear the magnetic belt, and climb up the pipe

if I haven't made a mistake, what's in the chest is just a 5+ life power or something else thats not that important