The Virtual Data Resource UI requires an element instance to display the transformation (right side of the screen). If you delete the only instance for a given element, the transformation is not displayed in the UI, but it has not been deleted. To display the transformation in the UI, create another instance.
Alternatively, you can access the transformation via API by calling:
Or for an account level transformation:
Note: if the transformation contained instance-level mappings, those were deleted with the element instance.