Actually I didn't really pin it myself - when I started MLWL in a browser, I got told that there was an app and it let me "install" it from there. I was under the impression that this really was a browser wrapper app, but obviously it isn't.
Now that you are talking about pinning a browser app I checked back on this and yes, this is what I did with the Memrise Community courses. That is, when you pin a browser (-link) to your homescreen, you should see that browser's icon in the lower right corner (on Android), as depicted by the left arrow (screenshot of my languages-folder):

Also, you'll see the browser icon in TaskManager. However, the MLWL icon is an app-icon without the browser icon, hence this is not a browser app.
Since you, @neoncube seem to be indicating that you never published an app (and I definitely cannot find it on Google Play!), this leaves me sort of flabbergasted as to what might be the reason.