Application runs, but I can't find the .app file (Pages, Numbers) If I open up a .pages or .numbers file on my computer (macOS 10.12.4), the respective applications open without delay.

However, when I search for Pages.app or Numbers.app in Finder, I cannot find either application! Neither application is listed in the Applications directory.

Where are these apps located?
You can check where any application is located via the Dock.

Right-click on the app's icon in the Dock and go to Options > Show in FInder.

If you haven't already got Pages and Numbers in your Dock, you don't need to add them. You can still do the above while they're running.