@Ana89: Sadly, if you have not backed up your phone to an external source then it will not be possible to recover any personal data that you have deleted. If the file is anywhere it would be in the Voice Recorder app itself *accessible by tapping the 3 white lines*, or in Apps > Samsung (folder) > My Files > Sounds.
Do you have a Samsung Cloud account registered with your S9? If so you could try restoring your last save if it occurred prior to deleting the file. If you can remember what you named the file, if applicable, then you could try using the Search function at the top of the Apps menu as another means of locating the file.