Can you cite a precedent? I think not! I can't even imagine such a thing - as a scientist.
I think that you misunderstood my point. I am not saying that it is proper for science to declare that something could never be explained by natural means, only that at the present time that it cannot be explained so. As for a precedent, at the present time science cannot explain the origin of life.
This might approach it from a tangent:
"The most incomprehensible thing about the world is that it is comprehensible."
- A. Einstein