We need to identify what list this is using.
First, lets check the layout (I'm assuming this is the Incident BO) for the self service user:
For me, it is the 'Incident Layout 0'.
Next, we should click into the layout and onto 'gridView' (or whatever it is named for 'List' type) to check what list that layout is using.
Click 'Edit' for that list and select the relevant field
You may need to add the field again/make some modifications - let us know how you get on