Setting the lookup field to 'Disabled' ( <Field>.Disabled = true) will not make the field readonly or disabled, it just prevent the editing of the entire row.
I have tested in both Row_Rendering and Row_Rendered without any condition, still the same result.
"Disabled" only means adding "disabled" attribute to the input control, the input control is still there. If you don't need to set it dynamically, you can set the field as "Read only" in Field Setup page. If not, you can also use Custom Edit Tag to use your own HTML markup. See Field Setup in the help file.
Otherwise, explain what exactly you are trying to show. Post your code in server event for discussion.
Sorry for the late reply, I have sent an email to support , containing a sample project to clarify my question.