I would think he left the sheath by accident ? In all the chaos ? I think this because he very soon after bought another K-bar knife and sheath directly after this crime, if I recall correctly ? He bought both knives from Amazon. I’m thinking he knows he lost that sheath, but in all the chaos and confusion, he does not know he left the sheath right by his first victim. Maybe in his misguided thoughts that he believes he is committing the perfect crime, he cannot possess a knife, without a sheath ? So he needs to buy a new knife, so he has the knife/sheath pair.
Now that I typed this out, does it even make sense ? Lol ? At first I thought there was some rationale that he would need to produce both a knife and a sheath in case he was questioned by police, ( he thought in his mind “educated” by his Criminology Class that he committed the perfect crime, and thought he could talk his way out of it ). However, if the police are even knocking on my door about a heinous murder I know I have committed, and i have a k-bar knife, with proof on my Amazon.com account I have purchased, not one, but two k-bar knives/sheaths, I know I lost the sheath somewhere ? I don’t think he knew where he lost it.
(I know I am too wordy, I try not to be ! I try to be more concise, it is a definite problem of mine.)