So how to start recovery process:
- Just boot your system normally and wait for windows to open.
- Just move your mouse(Cursor) to the right bottom and a screen will appear by sliding from right side of the screen, select Search from it and there enter the name of the program or app which you have lost from the start screen.
- Search for the program when you have found it right click it and then select pin to taskbar .
- Now you are all done and you will surely see the app on your desktop screen.
See related article about Default browser in Windows 8.