The Match UI should be able to detect if unapplied changes have been made and the Matchgrid needs to be rebuilt, and place an alert on the matchgrid management page. This would most likely be done by looking for the most recent modification time on any Attribute or Attribute Group used to configure the Matchgrid, and then comparing that with the last time the table was modified (either as asserted by the database if possible, or stored as a timestamp in the matchgrids table).