Note that the "missle" was "removed by Commander James J. Humes." That is, it was removed from the body during the autopsy, rather than received in from outside. It can't be anything found in the limo and delivered to Bethesda, as Young would have it.
BTW, while "missile" can in this context refer to a bullet, it can also refer to a bullet fragment, bone fragment, tooth, button, or any other object propelled through a body by external force.
Well then, it should be easy to find clarification in the official documents for such a major discrepancy.
Missile is a bullet, I'm not aware of any reference of other fragments found in this case called "missiles".
Even if "removed" Humes made no further reference to it, The document was hidden until 1972.
Find an official reference that missile means fragment would clarify it as not just another lame excuse