What I think he is saying is he built a 'map' thing, loaded it as public and then people built on it, then he saved, somehow the bricks were cleared. Then when he reloaded the save every brick was public.
The way to get around this is to save the 'map' you built as one name such as 'mapbase1'
Then you save after people have built on it something like 'mapbuilt1'
You would then load mapbase1 as public and after that fully loads, you would load mapbuilt with saved owner.
Hopefully this helps