For some reason or another, you can't get to the McGuffin because it produces a forcefield or has a forcefield surrounding it. Possibly due to it being a Loyal Phlebotinum or Empathic Weapon. Maybe there is an enchantment upon it that causes it to repel a certain type of being, such as demons, or maybe it's a curse that will let you touch the object but causes adverse side effects, such as death. Examples of Self Guarding Phlebotinum include: