Just because a thing can't be logged, charted and summarized doesn't mean it isn't real.
There are so many dimensions to this narrative that are salient to the point of the novel. Nothing about the murder of Gar can be logged, charted or summarized, especially prior to the discovery of the syringe. There is no way for Edgar to prove that he has seen his father, or that it is his father's ghost who has led him to find the syringe that was the murder weapon. But just because he cannot find a way to write this down, or catalogue it, does not mean that it didn't happen. In fact, the entire issue of Gar's murder is like this; it can't be logged or charted in any way other than as an unsolved murder, or an accidental death, but just because Claude has not been proven to have killed him does not mean that this is not the case.
An awful lot of the facts of this novel are essentially taken on faith. It's impossible to summarize the experience of seeing the outline of a ghost, or describing how this ghost caused deep smoke to descend in front of Claude and prevent him from leaving the barn, but it still happened nonetheless.
Half the time, we walk around in love with the idea of a thing, instead of the reality of it.
Much of the book is about illusion versus reality, and this is summed up in this quote. This extends to Trudy the most; she is in love with the idea of Claude, attributing to him many of the characteristics that her husband possessed, but the reality of Claude is something completely different. He is nothing like her late husband and for every good and admirable quality that Gar had, Claude has the opposite in just as strong measure. Trudy, though, is in love with the idea of Claude because he thinks he is like her husband and because being with him provides a continuity to her life that she is already missing. The idea of having a good man at her side is appealing but the reality of her situation is that the man by her side is anything but a good one.
