Slats,
It is the responsibility of the accepting ATC unit to initiate Comms checks in the event of a missed call, and after 15 minutes to initiate the appropriate SAR phase. These comm checks include coordination with the preceding ATC unit. Seeing the aircraft
a. stop squawking mode S,
b. cease comms, and
c. make an unapproved route AND level deviation,
surely would trigger DISTRESS in any mans language. The fact that a distress phase wasn't launched for 1 hour and 20 minutes after the transfer is an indictment on all involved, and no doubt has had an influence over the fact that this search has gone on so long with absolutely zero results..