The icon is in the bottom left corner of this screenshot. I am showing what is in my recents tray - what you see when you double tap the home button. That is what the icon looks like. It has to be on one of your home screens because you cannot delete it. Look on all of your screens and in all of your folders for it.
You can also reset the home screen layout and the icon will reappear - but the home screen will return to the way that it looked when you first activated your iPad.
Settings>General>Reset>Reset Home Screen Layout.