One interesting thing was that when I dropped out of the base of CAS, the EuroFPL (through which the FP was filed) tracking facility showed that Eurocontrol lost me too, and still showed me in flight some 10 hours later
I can see how this happens: ATC issued me with a different squawk when London Control dropped me. But even though the original squawk was restored (by Dublin) later, the flight was never re-picked up by the Eurocontrol tracking.