They were most probably already without comms before entering Belgium (i.e. over France). The French will report this to Maastricht Control and if no contact is made within a certain period of time the Air Defence chappies will make the decision to scramble. As I said, it's good fun for the F-16 jockeys on what would otherwise be another boring day
As for what the crew were doing, well I guess they must have thought it was another quiet day in some of Europes busiest airspace