Are you sure you do not have a "Recently Deleted" folder?
It is generally at the very very bottom of the list of your voice memos.
Other recovering options you may find helpful:
Restore from an iCloud Backup: If your iPhone is set to back up to iCloud automatically, you can restore your device to a state before the memo was deleted. Be aware that this process will replace current data with the backup's contents.
Restore from an iTunes/Finder Backup: Connect your iPhone to a computer and open iTunes (on Windows or older macOS) or Finder (on macOS Catalina and later). Select your device and choose to restore from a previous backup that likely contains the deleted memo. This will also overwrite current data.