We know that the Byakugan is the dōjutsu kekkei genkai of the Hyūga clan of the Hidden Leaf. And each village does its best to try and keep such coveted powers to themselves.
But in a recent filler episode of Shippuden, Episode 358 to be exact, a ninja from the Hidden Mist was shown to have used the Byakugan and could locate Uchicha Shisui, thereby asking his team to retreat. How does a ninja from a village other than the Hidden Leaf and not of the Hyūga bloodline have the Byakugan?
Is this for real or is it just another mistake by the animators? Is there a mention of such a ninja in the manga(I follow only the anime and not the manga)?