In one of those pictures it looks like Archie and Regina have a disagreement…maybe Archie disappears on purpose to frame Regina? Just a random idea, but probably won’t happen since Archie is ‘good’ and wouldn’t do that.
Orrrr maybe Archie can’t be found because he’s off doing something for Regina or something of a personal nature and [like it was said before/above] since the last person he is seen talking to is Regina everyone thinks she did something to him….cut to: end of the episode – Archie shows up and everyone is all….oh jusssst kidding 😆