The Philosophy of Time Travel
It's probably splitting hairs to point out a plot hole in a film like this, but how did Samantha obtain the copy of The Philosophy of Time Travel or Donnie's rabbit pictures if we are operating on the premise that Donnie was crushed by the jet engine? Wasn't that the entire plot of Donnie Darko - to undo the entire plot of Donnie Darko? Therefore Donnie never saw the rabbit, or got the book?