I get the same problem with this field. It doesn't show up in the admin interface, but when I try to save the object, it blanks the field and tries to update it in the database. Since the field I want hidden is a foreign key, the update statement dies saying "ERROR: invalid input syntax for integer."
I can get around this by adding a _pre_save() method, looking up the old value, and the setting it on the new object. However, this is pretty messy. Is there a way to get the field to display on the admin as merely uneditable text, then? The core of my problem is that the foreign key field points to a table that is huge (tens of thousands of values). When the admin page loads, it makes a drop down box with all of these values. Therefore, the admin page size is really large and it takes a long time to load. I would rather just show the text of the field or hide it altogether, without showing a drop down of all the possible values.
