Tony Cox wrote:

Did the Fokker roll back onto the runway?

No. After landing, he was instructed by the tower to leave the runway
and taxi to the apron via taxiway xy. Other than one would expect, this
particular taxiway is not controlled by Ground but by Tower, because it
crosses another runway. The Fokker crew was not aware of this but
thought "well, we're on the taxiway, let's switch to Ground". Ground
wasn't aware of this, because they don't care what's on this taxyway,
and Tower couldn't contact them anymore.

Of course the Fokker should never have entered that crossing runway
without permission in the first place.

For details and an airport map look at the link I posted earlier.

Stefan