Plugster,
Idle thrust for 40 seconds on the approach is not realy an issue. On a jet aircraft like the 73, it is common place for the crew to carry out continuous decent approaches. During a CDA it is normal to have lengthy periods of idle thrust. The question is, why did the crew not notice that when the speed had reduced to what they had selected, did the autothrust not start to come back in?
I don't believe that a hand on the thrust lever would make much difference in this case, you either notice it is time for thrust, or you don't.
Framer,
If you are handeling the aircraft you should cover the controlls, no need to have your hands welded to them.
If you fly the 73, I would be amazed if captains don't regularly ask you to remove your hand from the thrust lever in order for them to ensure the correct flap selection.
While your left hand is glued to the thrust levers, who is making all of your MCP selections while the autopilot is still engaged?