If you haven’t tried to restart the device yet, give that a try. Press and hold the “Power” button, then select “Restart”. In many cases, the Home screen will refresh and the icon(s) will return.
- Ensure the App is Not Installed to SD Card
Sometimes, apps will disappear if they are installed to the SD Card. Try moving the app back to the memory of the device under “Settings” > “Applications” > “Manage applications“. Choose the app that goes missing from the Home screen, then “Move to phone” or “Move to device” button.
- Reset the Home Screen Launcher
This step will reset your home screen completely and is only recommended if disappearing icons is a continuous problem. “Settings” > “Applications” > “Manage applications“. The app name will differ depending on the device. Looks for something related to “Home” or “Launcher”. If you have a Samsung device, it may be called “TouchWiz”. Select the icon, then choose “Clear data“.
For more details check Lg G4 Manual.