Grab AVIDemux and create a 20 minute video by appending the 10 minute video to itself and saving.
http://avidemux.sour...ge.net/download.htmlOr you can use ffmpeg to concat the video:
ffmpeg -i "concat:input1.mp4|input1.mp4" -c copy output.mp4
If you've got access to Linux, (or use WSL), then you can also try
untrunc.
BTW, it mentions that if the 'good' sample video was from the same device/source as the 'bad' video, then you'll have a higher degree of success.