Thanks all for the kind comments. Many thanks to Scantron, Dr Hysteria, Eta Carinae, Agent MacLeod, Dr Leonard, sirpudding, Decibelles, manofdoom and weizhong for encouragement and feedback on the draft.
I agree that the last line (and the whole final note) is difficult. I had many different versions, as those on the forums can attest, and this one was last minute, and arguably a change of tack.
I almost cut the whole note for a downer final addendum that noted that the creation of white space had slowed to a stop. On balance, I think I prefer Dr Harper still out there, searching.