Well, it is possible the app icons are still there, but got combined with other icons to make a 'folder'. So I would check the different icons on the device to make sure that isn't what happened. All you would need to tap an icon on the screen and see if it loads the app only or if it shows more than one icon to choose from. If it is showing more than one, then you would need to separate them to get them the way you had them before. To separate them you tap and hold the icons that are combined and then drag the one(s) you want to move away from where they are to a separate part of the screen.
Now if they aren't combined, or aren't on a different home screen, then you would need to readd them to a home screen. To do so you just need to...