Run a spotlight search. When you close it, it will be where it had been before.
I once somehow lost the Settings app, and was going nuts looking for it. I ran a Spotlight search and when I closed it, there it was, on my homescreen.
Where is it? If it moved to the 2nd screen page, long press the icon and move it toward the first screen page and pull it way over to the left and hold it. It should go back. It's tricky.