And amazingly it was still there, sitting on the seat where I'd left it. This strikes me as little short of amazing, since over the years I've lost (from this and earlier bikes) the BMW badge, a mirror, a clock, the road tax disk, and the plastic cover over the big bolts that hold everything together. All of that stuff was fairly firmly attached, the helmet was just sitting there.
This is undoubtedly the prelude to something horrible going wrong!