Genius Loci is not a native app. It therefore does not appear on the Apple App Store or Google Play.
This has many advantages: for example no need to install it, but the drawback is that the shortcut icon does not appear automatically.

It is, however, very easy to add a Genius Loci icon to your phone.

On iPhone, once on your Place, tap the small arrow at the bottom centre of your phone. Then tap “Add to Home Screen” and the shortcut appears.

On Android, depending on the device or browser, the option may be called: “Add to Home Screen” or “Install App”