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I have seen the app icons disappear from time to time on android phones while the apps are actually still installed. First of all reboot your phone. Then, check to see if your apps are still present. I would use a file explorer, but at least check your “app drawer” on the bottom of your home screen and look for the missing apps. If they are there, just replace the icon by dragging them back to your home screen. Alternatively, you can go into settings>applications>manage applications and you can see what apps the OS is recognizing. While you are in APPLICATION SETTINGS, make sure that the box is not checked that will allow unknown sources to install applications. This will help prevent software from being installed without your knowledge.
You might also consider installing either AVAST! or AVG Anti-virus and running a full system scan. It’s much more likely that you installed malware than your Android was actually hacked, but I guess to some degree that’s just a matter of semantics. If you installed any new apps around the time that this issue started to occur, I would suggest that you remove them as well. Check the feedback on Google Play for each suspect app. Usually apps that contain malware are pretty quickly identified by users on Play. You can always reinstall them later if they check out and/or the problem persists.
Worst case scenario, you can always do a factory reset. Good luck!