I also clicked download later when getting a digital copy just about 20 minutes ago. Then decided maybe I should download it since I didn't see it in my Movies list.
I've verified that the steps above do not help. The only place I can find any comment about the movie is in "Purchase History" where it shows as FREE. But I cannot download from there.
This is using iTunes 11.0.5 (5) on Mac
My movies library does show other movies from the cloud, but not the one I just unlocked. If I go to the movie in the store it wants me to pay for it.
There appears to be others having this same problem that you click download later and then can't find the movie.