When you start the tool and open a design everything opens automatically. Is that true? The physical model will not be opened automatically. You must go to Physical Model, right click and Open. And there it is again. So do not panic if you do not see your physical model, it is not gone:)
The reason for not opening the physical model is performance. Usually the physical model consists of many, many xml files and if all those files should be opened on opening the design you might get bored before you are able to use the tool.