vanishing displacement maps shortly after baking While working in Blender 2.72b Internal mode, I built this simple model  

I used these settings to bake the displacement map  

I got this result after baking and using the Displacement Modifier, along with a few more modifiers... Note that I applied the Displacement Modifier shortly after I set it up.  


OK. So I was happy with the results I was getting in my initial study, so then I decided to keep building on this process. I built a more elaborate model, set up like this:  
here are my results with a few more modifiers in the stack



Some time passes as I work with the model. At this point I make a full copy of the scene so that I can branch off on a new idea with these current assets. I bake the previous model the same way I have been, with these results:
 


At this point I want to move to Cycles Mode so that I can start building materials, light the scene and give it a render.
Now I am in Cycles with a material applied, lights and camera set:



Here is the result of the rendering:


I know it's not pretty, but when I came back to the project a little while later, all of my displacement maps have vanished. My models and displacement maps look like this:


and



I have been working through all of my steps again so that I can capture screenshots and write this post; as of now my second set of baked Displacement maps have all turned black.

Are displacement maps temporary, only to be applied shortly after baking? Or is something happening after switching to Cycles, and then rendering?

Does anyone know what is going on here? Is this a bug or a known feature?
Any help would be great, thank you.

-Joshua

ps. sorry for the long post, this was just not a good user experience for me and I want to help improve it.
You need to save all images (also created textures) to an image file F3 (Menu: Image / Save As Image) otherwise all changes are lost. Blender indicates an unsaved texture in the UV-Editor with an asterisk at the Image Menu Item.



Another option would be to pack the image into the .blend file.