Restore Building in Minecraft PE
If you are using it in creative mode with cheats on you can build an identical build elsewhere and use the clone command to replace it. I can't give you an exact command with all the tags available because I don't know the coordinates and the size of your structure. If you have already built the structure try cloning it elsewhere and set up a command block that clones it and hook it up to a clock that does it every minute or something along those lines. If you are not using cheats or not in creative mode then you can't do anything about it.