Although jeremy lost his left leg beneath the knee, he often experiences great pain in his left foot. this is known as

"Phantom Limb Syndrome," the sensation of a body part that is no longer present, but feels like it's still there, is most often due to limbs, after amputation or traumatic destruction. It is due to the cerebral cortex still trying to "make sense of" a limb that used to send signals to it.
When it is painful, it's called "phantom pain" as such.