Preferred category disabled

We're using canonical URLs on products in SiteBuilder. The category used for this is derived from the preferred category setting in the product data, as per Netsuite's recommendation. This generally works fine, but we've recently noticed that if a product is in multiple categories and the preferred category is subsequently switched off, the product listing is not updated. This then results in the product having a canonical URL within a parent directory which 404s.

I'm trying to create a saved search to list Product Code > Preferred Category  > Preferred Category Display Status in order to locate any affected products, but I can't see any way to get the last column to display whether the parent category is active. Can anyone shed any light on an easy way to achieve this?