Janskeet said:
Okay, he's able to read people's his mind but can't find Luke in an almost completely vacuous area?!! Lets not forget that Palpatine found the exact location of burnt Anakin on Mustafar using only the force to find him. I know they're just B-movies, well the prequels anyways, but this always bugged me.

Factors to consider.

Palpy KNEW exactly where he sent Anakin on Mustafar. Anakin was still in the same factory/complex where he killed the Seperatists.

Anakin WANTED to be found, similiar to Luke wanting to be found at the end of ESB. Luke didn't want to be found. Maybe instead of 'vanishing' in the force, he was just not broadcasting actively.

On the other hand, perhaps finding someone with the force has a limit of specificity, like using GPS. Maybe Vader could sense Luke was in the room, but no more specific than that. That possibilty explains how Leia found Luke, Palpy found Anakin, and Vader found Obi on the Death Star, but why Vader couldn't pinpoint exactly where Luke was.