This is a bit of a stab in the dark, but have you tried saving as a DXF?
The beauty of DXFs is that they can be opened up in a text editor. I've seen guys edit entire DXFs in Notepad to change block names, then resave and whooshka, when they open it again all the blocks are switched out.
Anyway, I am guessing your wall data could show up and even be manipulated in the same way.
Cheers,
Link.