I still think that some internal organs (most likely intestine) had to be at least clipped. The question is if they were do they heal on their own and at what rate?
My ONLY point (evn though I think the arrow DID go under the spine) is....exactly what you state, above. HOW cn you have an exit wound from a pass-thru THAT ow on a deer's body....and expect that no internal organs were hit?
What do we tell EVERYBODY about gutshot deer? They WILL die from their wounds.