So, did the whorehouse sister just pull a Chuck Cunningham?
Mia Kirshner (Kenya) was listed in the main titles -- as was Trenna Keating (Doc Yewll) in the first-act credits, even though neither actress appeared in the episode. It's not unusual these days for the "regular" cast members of ensemble shows to skip an episode here and there, since there are just so many characters to follow.
And, conversely, an actor can sometimes be listed as a guest-star and yet appear in every episode!
(Richard Thomas has appeared prominently in pretty much every episode of THE AMERICANS so far, but is still listed in the opening credits as a guest-star . . . which makes me worry about his character's life expectancy!)