In other words, the layers themselves from my Photoshop file are missing, and I have no idea where to point After Effect's "Replace Footage" feature towards to find these constituent layers.
Use the OS to search for the photoshop document. You can figure the new file path from it.
This is also a good lesson in developing a standard organizational system for every AE project, and sticking to it.
ANSWER: Nevermind. This is no longer an issue in After Effects. I'm running After Effects CC 2015. All you have to do is:
1. Find your project window. At the top in the search bar, type in "missing". This will expose all your missing files
2. See the missing, individual embedded layers before you. Select one, any one, and right click it and chose "Replace Footage>File".
3. Now simply point this sub layer in the direction of it's parent file (probably a Photoshop file or an Illustrator file in any of our cases here) and After Effects automatically populates everything as it should be. ***THIS is the part that tripped me up. I was hesitant to point/replace/reload an individual missing layer to an entire PSD file, fearing that it would, of course, replace ONLY THAT layer with the entire PSD project! But...it appears so far, that this is not the case...After Effects seems to be intelligent to know what I was going for. Rock on!
Either this has always been a workaround and I didn't know about it, or it's a new feature, or I just did it wrong and won't know until it's done rendering!!!!! I'll post back and confirm that this method does indeed solve my initial problem.
Most definitely, Dave about keeping things organized. I'm an organizational FREAK (had a very strict professor many years ago in college who forced us to utilize a particular method of organization, applied to anything, and it stuck!). What this was a case of, I'm afraid, was a terrible sleep schedule. I pulled 2 all nighters on a project and frankly have almost no memory of last night! Deadlines, deadlines, deadlines... Thanks for the input. You're amazing!