The closest I every seen the FA's not prepare the cabin for landing was actually just a few weeks ago on the 789 flight ORD-DFW. We were about 10 minutes from landing and the pilot announced to prepare for landing.
They all jumped and hustled like crazy to get it all picked up and away, I think they were genuinely caught off guard by the short notice.
(overall, it was a great flight crew too at least in J, lots of drinks poured, several rounds of snack basket being passed around (which was left out at the bulkhead seats for anyone to grab what they in want between rounds), and very friendly and hard working crew.