Someone may have enabled Restrictions in your friend's Settings app that is blocking the use of the camera (and from seeing the icon).
To see if that is the case, go to the General tab in Settings and press on the Restrictions line on the right (if Restrictions is on, you will need a password for the tab to open). If it is on and you've entered the password, check to make sure the Camera line under "Allow" is turned ON.
If that works, yay. If not, holler back and we'll take another shot at it.
Marilyn