It may be possible that she was hit by a car and had some internal injury's. Did you notice the abdomen bloat prior to the shot or after
you returned to retrieve her ?
Are you in a state where CWD has been confirmed if so you should have contacted your local DNR officer , that still might be a good idea
they may even be able to tell you if there has been a car deer accident and the deer was never found.
All possibilities.
Bill