It does work, you just have to read the instructions!

I decided to rate this app (something I rarely do) because I was almost misled by the low (well, in my opinion) score on the App Store. I found that people were complaining mostly because the app couldn’t recover files from mounted drives but only from images. That is not totally true. If you click on the ‘Instructions’ button when you first launch the app, you will read that in order to immediately scan and recover your files from both the internal drive and mounted drives, you will need to install a very small helper app (around 600 KB) which is freely available on the website. Once you do that and relaunch the app, you’ll see all your drives visible within the app and can scan them. Thankfully, I kept on reading the reviews and found a helpful one that explained all this. All you have to do is read people! Five stars, especially since I got this app for 1.99 euros! Great deal!

Khillo about Disk Drill Media Recovery, v2.5.432