Hi and welcome to the Forum!
I have given your post it's own thread so as to help you better and not to interrupt the other ongoing thread you had posted in, which by the way is against those pesky rules of ours.

. So please start a new thread for any questions you may have, that is after doing a search first.
Now to your question.....the app must still be on your iPad if you can access it by way of the App Store. Are all your screens full? Once you fill all the available screens on an iPad any extra apps you then download will not be shown, they are in the nether somewhere and can be accessed by doing a Search......the answer to this is to make some folders so as to free up screen space.....other apps you have downloaded will then show up.
If this is not the case could you have inadvertently changed it's screen location? Once a screen is full it will kick other apps to the next page when you are moving apps around.....it's a fairly easy thing to do by accident.....so have a look on each screen.
If still no joy, try a reset of your iPad and see if that makes a difference.
Reset - Hold the power off button and the home button simultaneously, keep holding them in and you may see the power off slide appear and disappear, wait until you see the Apple logo appear before releasing the buttons. It will take a little longer for your iPad to start.
And just FYI.....you can search your iPad for apps by placing your finger in the middle of a screen and pull down on the screen.....a Search tab will appear at the top of your iPad.
Let us know how you go.