I was too busy talking Burms and Retics and asking about the tail slipped my mind, while we were talking in person.
I did email him, last night. At first, I was under the impression that he'd had this Savvy for the entire 4 years. But, he said he bought it from his brother in law...whom bought it already with the stub tail and scar on its back.
So yeah...it's definately a very old wound. I thought it was probably a sibling, who got a little over anxious.
It certainly doesn't slow him down...this little guy can move.