The changes that you make on the RadDiagram control are saved only on the client, so it is expected that the ShapesCollection will have the initial shapes.
There is an option for exporting the diagram data as shown in the following demo: http://demos.telerik.com/aspnet-ajax/diagram/examples/saveload/defaultcs.aspx
. Nevertheless, currently it has a bug with getting the information for modified connections. You could use the following bug item in our feedback portal to track the status of the issue, vote for it and comment it: http://feedback.telerik.com/Project/108/Feedback/Details/139644