How about a functional flight monitoring system where the airline would have a qualified, trained flight dispatcher with a separate communication system that can contact the aircraft with SELCAL and/or ACARS along with an aircraft situation display that shows the position of the aircraft as it proceeds? If ATC loses contact, then this system could be used to confirm the aircraft's position and have the crew contact ATC. It would avoid situations like this as well as provide the crew with much better information regarding weather, atc, notams, etc, while the flight is enroute. It is terrible that ACARS is turned off.
If you remember, a similar but worse situation happened last year with Air Europa from Norway to Spain where no less than 6 interceptors (3 sets of 2 aircraft each from 3 different countries) were scrambled to find the aircraft after it was lost by ATC.
The truth is that when this happens, not only ATC doesn't know what is happening but neither does the airline.
Each airline should have its own flight monitoring and communication system to support the crews properly. They should know where their aircraft are and have a system to contact them.