Holes in the brain

This is a comment on Pedro's blog, but so you should know the worst I put it here too:
Visual memory is perhaps not the worst to be lacking. I have no spatial memory - not in the sense that I can't for instance rotate 3-D shapes in my head, but in knowing where things actually are. Yesterday I was explaining the shape of the house (an old mill building) to a friend. Suddenly I was puzzled. I pointed to a wall and asked my wife, "Surely the bedroom above can't be that small."
"What do you mean?"
"Well.." I gestured at a small space inside the front door, "that wall..." (I assumed the bedroom was the same size as the space I was looking at).
"And," she said, "what is beyond that wall?"
"The house next door," I said (with that "of course, do you take me for an idiot?" intonation.)
"Well, go and have a look," she said.
"What, next door?"
"No," she said, "into the study."
I didn't have to. At that point I remembered that in the study, where I am sitting now and sit a substantial part of the day, is a sort of anomalous stone platform to my right where I keep my two road bikes. It is where I gaze absently when nothing else is going on in my brain - that is, a lot of the time. And yet in explaining to my friend the layout of our house, in which we have lived for sixteen years, I had entirely forgotten about this 1.5 metre wide platform, and subjected our spare room to a procrustean fate, cutting 1.5 metres from it's length.
My wife gave me that look... those who have been together a long time know the one. Not despair, exactly, and, you hope, tinged with affection.