Use to see what the actual package name is. dpkg -l lists all the packages the dpkg utility has installed (which means everything installed with the app managers, apt-get, or dpkg -i, etc), and grep then filters out all the lines except those which contain the string "flashlight". If that doesn't find it, try using just "light" instead of flashlight, or something.

Running this on my device, I get the package "flashlight-applet". So I think that's the proper name of the package. So try pinning that.