"No doubt it will move again in the future, perhaps in May as December and May are frequently the months the satellite is moved"
I was very right with the "perhaps in May": PAN is on the move again!
Greg Roberts observing from South-Africa noted it missing at its old position on April 29.
Ian Roberts, another South African observer, then located what likely indeed is PAN near Intelsat 12 on May 6th. Greg Roberts then managed to find it in his earlier images of May 4th as well, confirming Ian's observations.
Just goes to show that even the most secret of all satellites cannot escape the inquisitive eyes of a dedicated amateur.