If the bone is table scrap, the only thing that comes to mind is
redeposition.  You may have found evidence of fill being taken out of
one place and put in another; possibly reuse of an older, filled hole.
I think this would be unusual, so your analysis and findings will  be
interesting; keep us posted.  Is there any animal activity in evidence
on the deeply buried bone?  Anything to indicate it was ever somewhere
other than 10 feet under?