This is another example of the intransparent game mechanics.
Thats NOT to meant to be a criticism – in my opinion it is, i'm not kidding, actually displaying the realistic character of the game.
Even if the mechanic in that case was not intended to work out that way, could be some kind of bad luck...
Its hard to decide where a player should immediately get information and feedback from his action. In this game, consequences of player's actions can often be completely unnoticed, just because you are doing a lot of stuff. i mean, like IRL...
Of course, players have to get some kind of feedback, to make wise decisions.
I think there is still some finetuning to do, to see if some random actions produce irrational or even unrealistic("wrong") results ingame. I think that is work on a micro-scale, that can only be done by the devs. And it only pays out if the problem is big enough, because obviously the bigger problems should have the highest priority.
I can try to deliver some explanation for your particular situation...
1. If there is no evidence for another thing, I really would join JEB Davis in his assumption that the dog had been from the village.
2. Did u skin the dog in front the people or near the village?
3. Could the njerp have looted a dead villager in the fight(e.g. picking up a better weapon), or did he carry arrows that had been shot on him?
To summarize, could there be any items proprietary to the villagers in your posession, perhaps you traded or discarded, or have eaten?