I was recording and video on my phone when the battery died, how can I recover the video file?
I had the same promblem. A solution which worked for me was an app "MP4Fix", which you can get in google play for free. It repaired my video in a few sec and placed it in different folder (it kept corrupted video in the same place and also created new repaired one). 
I know this info might be too late for you but it might help some others.