Whatever program provides the Fn+Sym popup seems to just crash from to time, and then Fn+Sym does nothing. I find it happens to me randomly when text messaging, every few weeks. Eventually it comes back, but it's quite variable how long it takes to decide to come back. A reboot should bring it back always. (If that doesn't work for you, you have a different reason for it not working than I do.)

To see how bad the secondary camera is, and why you probably don't want to use it, you can try the Mirror app (it's awful on mine, noisy, colour noise, banding, and can't see anything unless my face is directly lit). Also Skype may use it for video calls, but I haven't tried so can't confirm that.

(On the optimistic side about picture quality, BlessN900 and Fcam apps show that software & drivers make a surprisingly big difference to picture quality. They take noticably better photos with the main camera than the built in Camera app. So in principle the secondary camera might be improvable through software.)