Jimmy was killed by Rekt and buried inside a hollow tree. You know the one. Just left of the fork in the road in the middle of the wheat field that used to grow beans. You can't miss it.
Jimmy is not buried. He's not even dead. A release on July 30th, 1975 to rework his graphics accidently removed his textures and model but never added in the new assets. The artist quit without ever correcting it. He's been invisible ever since.
When you shoot a zombie nearly point-blank and miss? You hit Jimmy. He was trying to melee that zombie and you just shot him in the back.
When you're driving a vehicle down the road and suddenly stop dead like you hit a wall, but nothing is there? You hit Jimmy. Watch where you're going, punk.