I think it's really interesting that the author chose to include this poem he had written and then write multiple reasons why it was wrong. Is this what he actually remembered? If it is, how did it get so off target? How memory in traumatic situations like this works is still kind of a mystery to many people, which makes witnesses to criminal activities so difficult, but I think part of what he is showing here is that there are so many things that can go awry in the brain and uses it in a direct contrast to the physical lump in his head.