The load action extension attribute "retainmodels"
The xforms load action instructs the browser to navigate to a new location. By default, this action unloads the form engine by firing the xforms-model-destruct event. If the form state is needed after the load action (for instance if the load is used to show a preview) use the extension attribute retainmodels.
<xf:load show="replace" resource="/preview.aspx" retainmodels="true" />