Hillary and Thomases were talking about the raid on Foster's office where documents and his hard drive were removed. That is why the body had to be found in the park. Had it been found on White House property, the FBI would have been in charge and sealed his office. Some time later, Foster's computer was found in government service used by another federal employee. It had a new hard drive.
I still don't think Vince was whacked. But I do think his body was moved.