Today you still can find it, but you’d have to look more patiently, and not on the official resources. It is not surprising - unfortunately, the mapper apk was removed from many places it was put forward on previously. People who want to install the mapper extension software today often run into the problem that FB friends mapper doesn’t come up for extensions.
Facebook friends mapper Chrome extensions If you really need to see that patch of hidden friends, you will surely succeed in your research. Although it is not free and you have to pay for the license key, we are pretty sure that if you seek attentively and patiently, you will be able to find the free key (however, you would really have to spend quite some time, as it was removed from most of the websites).
If you do not know the location of the mapper, it is in the Extensions shop.