Missing Evidence
This is to solicit ideas on what are important pieces of evidence which we know or have good reason to know existed at one time but are now lost.
Two items come to mind. The first is the first shot. If it missed the limo where did it go? The second is the missing autopsy photos and films. Seems to me the evidence is strong that what we have seen so far is not all of the film that was exposed that night.
What else?