This did the trick for me. I downloaded the digital copy (using the code that came with the blu ray) of Expendables 2, several months ago. I've had it on my iPad since the day I downloaded it, but somehow it disappeared from iTunes on my computer and it wasn't in my movies list on my Apple TV.
I went to my account, and in the "iTunes in the Cloud" section, there was an option to manage hidden movies, music, etc. Clicked "manage" and, lo and behold, Expendables 2 was listed as a hidden movie. Clicked the "unhide" button and, voila, it showed up in iTunes and on Apple TV.
Thanks for the suggestion!!