First you should check your location of stored recording. Open the app, and go to app Settings > Recording > Location of stored recordings. The default location should be in “Recordings” folder inside your primary SD card or USB storage. If you have changed the recording location, you should go to the correct location where you stored your recordings.
Sometimes, people moved their files without noticing it, or change the folder name (from the default one “Recordings” to something else) so the Hi-Q MP3 Voice Recorder does not see the files again.
Name of recording files starts with “recording-“, followed by 8-digit date (YYYYMMDD), a dash “-“, 6-digit time (HHMMSS), and “.mp3” (or other extensions following the Format setting), like “recording-20150607-120024.mp3”. I hope you can find it somewhere on your phone or SD card.
Use apps like Solid Explorer or ES File Explorer to help find the missing files.
Make sure you do not install questionable apps that “clean junk files” from your phone because they might cause deletion of files unexpectedly.