Thats not true…there is a way to get them after deleting. This is a workaround to get this deleted XI Objects.
After deleting some XI Object its only important to know the Namespace and Name of the Deleted Object you want to receive. Than you can get want you want.
Step 1: You have to create a new Object with the same name in the same namespace of the Object you want to receive.
Step 2: Activate the New Object.
Step 3: Open the History of the Object and now you see the old Objects before deleting.