Genius Loci is not a native App. It therefore does not appear on the Apple Store or Google Play.
This has many advantages: for example no need to install it, but the disadvantage is that the shortcut icon does not appear automatically.
But it is very simple to add an icon Genius Loci on your phone.
On iPhone, once on your Location, click on the small arrow at the bottom center of your phone. And click on “Add to home screen” the shortcut appears.
On Android depending on the models or browsers, the option may be named: "Add to home screen" or "Install App"