I forgot to say that the uv's don't really disappear when you do a new planar projection map. Actually, I discovered that even though they seem to have entered the nether world, they truly haven't gone anywhere. When I click my mouse button over an area in my perspective or orthographic view, wallah, they suddenly reappear in the uv texture editor. I also discovered that all primitives are already unwrapped. So if you make a primitive and open up the editor you will see the uvs already unfolded. If you select some faces in a camera view, assign a shader and a color to those faces, and then select those faces for projection, those faces, or rather the uv's associated with those faces, will appear in the uv editor. These selected uvs, if moved in the editor, are no longer associated with the primitive. They stand alone. This was an easy way for me to see how uv's can be selected and moved. Now if I select an edge in the editor, one from say the uvs I just moved, I can select its corresponding adjacent edge. If I select that edge I can see how it is associated with an adjacent edge from another side of the cube. I hit move and sew uvs and those edges snap together. I'm done. A thing of beauty. This for me, was an easy way, to see how the uv editor works. I didn't have to unwrap a three-headed monster, do five projections on it, and then try and sew them all back together. I think I could actually begin to do such a thing because I taught myself the basic foundation of how the editor functions.
Carry on good fellow Maya maniacs....