Exactly: the bicycle itself has become an external, physical, extension of your internal memory, sort of a recording of you.

As for nostalgia itself, some old French medical texts dating back to the 17th century actually list it as a wasting disease of the soul that, if left untreated, can gradually remove all interest in living in the present; your family, wife, children, duties, etc. The afflicted looks continually back, to childhood, to friends long gone, to past glories, yearning for and yet unable to recapture the glow of those days until madness sets in. I'm paraphrasing, but that's the gist of it.

Who'd ever imagine that your own memory could be so dangerous?