#1. The link between the two tables would be better if it were not a field in use (autoenter Serialized ID). Surely you'll come across two people with the same name....
#2. Look from a layout based on your "specific information" table...put the ID key from your contacts table on it, and do a find for Contacts::UniqueID is blank from the perspective of "specific information".
That will leave you in a found set of "specific Information" that has no Contact associated with it.