Your imagination is getting the best of you. It's just an old bike.
Bingo.
I honestly don't get the whole 'ghost bike' thing; I'm not even sure I've ever seen one (maybe in Brooklyn once). I understand it memorializes a bicyclist who had a fatal accident, right? But is it supposed to be his/her bicycle? I, for one, would not want to be memorialized by either by a junk bike (because junk is junk, after all), or by one of my own bikes (because they are not junk, thank you very much). Nor do I want derelict bicycles to be chained up on public property. So... clean it up and ride it proudly!