Voice Recorder HD automatically closed and did not save voice memo after a long recording. This problem can happen if the iPhone/iPad memory is very low. Generally data does not lose in this case.
You can find the file using iTunes. See the instruction from following link how to see recorded voice memo files using iTunes. To see step by step guid for iTunes File Sharing visit following url.
1. Look for the file name with time you was recording.
2. If the file is available you are lucky. Now transfer to computer and try to play.
3. If can’t play then download following “Audacity” application from following link. It is FREE.
4. After completing the installation open the file from, File -> Import -> Import raw data
5. Select the broken file
6. Save the file with default settings. And play with iTunes.
7. If you want to import repaired file into Voice Recorder HD then follow the instruction from following link.