I expected this would be the case, but we should never give up hope on our animals, where there is life there is always hope.
You will be feeling pretty deflated at this point but hey! there will be a next time very soon so keep your chin up, this type of thing is all parts and parcel of keeping rays, we take the rough with the smooth, there was absolutely nothing you could have done to change the outcome in this case, the pup was born too early...... simple as.
I wish you all the luck in the world for next time.