Surely there is a backup. You can actually download the original world but it is about 1TB.

I think it would probably happen again if they restore the original version. Here is a comment from danish GeoData Agency spokesman:

"We consider that as a nature of playing Minecraft – elements are broken down and new are being created. Therefore we will not reboot the demonstration of Denmark in Minecraft. But occasionally we will rebuild minor areas if buildings are removed and nothing new is being created."