When I purchased a flight a few weeks ago for December in CW on a 777 every window seat was taken.

So I took 12D. An OK seat, but I would much rather have had a window on this overnight flight.

But I decided to take a peek at the seat map today and 14K was available! I think on this aircraft (ZZZ series) it will be missing a window but as this is an overnight flight in the depths of winter I am not too worried.

Moral of the story: if you do not get the seat you want then if you check again it might be there!