I much prefer the earlier episodes of Gunsmoke. I think the series worked better in the half hour format, but let's just say I like the B&W episodes. This was a good episode, and one of the earlier ones that made it clear that the ensemble cast could carry an episode without James Arness.
He had already started to reduce his participation in the show, a tendency that would grow, and continue to the end of the series. Chester was a great character, and it was the show's good fortune that they were able to find Ken Curtis, as Festus, to take his place as the marshal's side kick.
There was much less (mainly none) attention paid to tying up loose ends in series TV in those days (this was 1964). I can't be the only one who finds the handling of Chester's disappearance frustrating at least, and an insult to the memory of the character. An episode that included a story explaining his exit would have been not just appropriate, but probably wildly popular (during sweeps maybe?).