It's possible that leaving the cockpit to ground channel open (assuming it wasn't...) could have prevented this.
The ground engineer would be used to hearing the start calls (there should be little other chatter at this stage) and would thus be in the loop with what the cockpit crew were thinking. He would normally hear the second engine start, a pause whilst the flows are conducted then a clearance to disconnect. Hearing a request for the A/S checklist and a request for an airways clearance call would prompt him to pipe up to say, "I'm still here!"
I'd be interested to hear ramp guys' thoughts on this regarding the likely levels of distraction.
Out of curiosity, what is the SOP for when to put the INT switch to INT?