Undeleting a 5DIII movie file?
There's a free app that runs in the terminal in OSX that recovered some data for me. I think it's called TestDisk. Not sure if it will work for you, but I think it recovered some movie files for me. Not 100% sure since I was mostly trying to recover jpgs.
|Blue and yellow in water by fireplace33|
from Ink and water
|Kylmä joki kopio by Kaappo|
from Shutter speed 1/25 or slower
|WR_2.8_13 copy copy by photoprof|