I think we should all be careful of hanging our argument on one unknown, such as this, be it if we are Evolutionists, Creationists, or Theistic Evolutionists (like myself) because if this one point breaks, so does the argument. A gap in knowledge doesn't represent proof, it only represents a gap in knowledge. How long did young-Earth Creationists use the degrading magnetic field as 'proof' of a young earth before we knew that it fluctuated? How long did Evolutionists use Piltdown man as 'proof'? Science involves evolving (for lack of a better term) knowledge.
Some researchers never did buy into Piltdown. It was primarily the British researchers who were fooled because that was the set of traits they were looking for. Folks working in other areas of the world were expecting a different set of traits and it turns out they were correct.