Bug in a purchase realm from the store

My friend bought a Minecraft world off the Minecraft store Original One Block Challenge by Lifeboat it was working fine till it gave a obsidian with a sign saying go 250 block with a arrow pointing north of the block then when he destroyed the obsidian block it didn't replace the block like it should have so we decided to build 250 block north like it says but there was nothing there we decided to go into creative mode to see if we could find anything but there was nothing to find at all