So the phone basically crashed while it was recording the video. There's two things you've possibly got here, one the video file is there, but is incomplete and damaged. or two it wasn't written at all, but it just showing a file name, but there's nothing there.
Check how large the file is in the file explorer? If it's like zero bytes or just a few bytes, there's probably nothing you can do, it's not there and wasn't written before the phone crashed. On the other hand if you think you have the video, it might be showing several megabytes in size. It might be just damaged and needs recovering if possible. Do you have a PC? Try copying it to the PC, and see if it will play in VLC, which is a good media player for damaged and incomplete media files.
VideoLAN - Official page for VLC media player, the Open Source video framework!