MG23,
I'm sure anyone who may have received a communication from the aircraft was checking their logs on Sunday, but any relevant information takes time to percolate through the investigation.
I understand but what seems to make this a bit of a long time to search is that, as noted in earlier posts, these communication devices have the equivalent of a MAC or IMEI address allocated based on the airframe.
This would, I imagine, make searching the logs much quicker as there would be an identifiable characteristic to a ping.
I also wonder if one can use triangulation or simply dead reckoning from the satellite(s) contacted to get a feel for where the aircraft went.