Get root package display is confusing

Hey,

I have an application which offers select options to search the customized data elements:

SELECT-OPTIONS p_object FOR gwa_tadir-obj_name DEFAULT 'Y*' TO 'Z*'.

In this way I select the demanded data:

SELECT * FROM  tadir INTO TABLE gi_tadir            

            WHERE obj_name IN p_object AND object = 'DTEL'.

For every found element I call the standard SAP method get_root_package.

The results I get on an alv. There is no problem with an error or similar. The confusing thing is that I get only displayed the elements which are beginning with 'Y'. If I give an certain element manuel in the select options, without the default values, which begins with z i get the right root package. Why it does'nt show me in the alv also all z* like y* elements? I have enough z elements.