"I would posit that the opportunistic laptop thief is somewhat unlikely to carry a separate laptop on which they will have installed tools that allow them to reconstruct cryptographic keys - or for that matter have a can of compressed air handy."

Anyone who is going to be performing this sort of procedure, would be coming more from the industrial/business espionage angle, than an opportunistic thief.

This will not rule out the possibility that an opportunist might carry around these sorts of tools to maximise his potential income from any swiped lappy.