Alice uses the last clue to clue number 4 to Cathy. This appears to be a Finesse on Bob's red 3.
Bob is now left with 0 clues, but forgets to play his red 3 and instead discards his chop.
What notes should Cathy write? What should Cathy do on her turn?
Bob is not forgetful, he deliberately discarded instead of blind-playing his Finessed card.
From Urgency Principle, blind-plays should happen as soon as possible, and if Bob just had blind-played his red 3, Cathy could easily play her red 4.
So this is in fact not a Scream Discard, because Bob's known play was from a Finesse, and Cathy might also have a red 3 on her Finesse Position (as an Ambiguous Finesse).
Therefore, Cathy should not Chop Move anything. She should blind-play her Finesse Position as the other red 3.