Ever since you can just walk through those buffs, I wondered whether there is a possibility for it to be inaccessible. Yesterday I finally had the Sphere appear in such a spot that once I accidentally stepped away, there was no way to pick it up again.
I would suggest either some way to turn on the world map without moving (maybe by holding Confirm), or to make it that those Spheres are only immaterial as long as you are facing them; then you could turn into them like into a wall and then pick them up.