When you double-clicked on the layer, you opened the LAYER WINDOW. You're not looking at the comp window anymore.
If something link that throws you, you need to take a look at this:
Good Stuff Within!
Double clicking on a footage layer opens the footage window. Effects only are applied in a composition. If you want to solo a layer you can see the FX in the composition window on only that layer. If you open the footage window you will see, well, just the footage. It completely makes sense. Simply close the footage window or switch to the Composition window to view your project.
These are Basics. Please go through the Help files to learn about the different panels in AE and what they are used for.
Thanks for your help Dave, I will definitely take the time to watch the video.
Thank you Rick (and Dave), I see my error now. Before when I clicked back on my Composition window, the screen was blank, showing only my background color. But since you mentioned it, I clicked on the Composition window and waited longer and sure enough, the blank screen loaded up my Composition, layers and all.