Thank you for posting.
FileMaker Pro won't match on empty fields. This is in part to be consistent with SQL join behavior.
It should be easy to work around this behavior by simply defining a value to signify that there is no Special Requirement such as "none" or " " (space). To set this up, you could do a find with "=" in Special Requirements to get all records with an empty value and then use Records > Replace Field Contents to add a value. You can then specify an Auto-Enter value for new records in the field options for Special Requirements.