I have this problem, I have a number of apps that are are not visible but I can still find them on the iPad search and therefore are still usable. How can this be possible? Where the heck are they hidden?
They may be on a different home page. From the main home page, swipe left (swiping right gets to the search page), you can move them around by pressing on them until they wiggle, then slide it where you want it (careful not to hit the little "x").
Also, if you have a 'lot' of apps, the iPad will only display so many screens.
When you run out of screen you can keep loading apps, but they have to place to appear. The usual solutions is to make some folders (drag some apps on top of each other in jiggle mode). There is still a limit on how many folders and apps, but it's much, much higher.