Bit like the Malaysian A330, engineer fails to remove items, however post that we do have multiple layers of responsibility from others to try and pickup on these issues post that. Do not rely on ground operators to pickup on these things, it's a bonus if they do, however I have seen a Captain fall into this situation before, who got into serious trouble from the training department when the ground crew reminded them about something that they failed to pickup during a preflight.
I don't believe the Roo has engineers dispatching flights from the stand anymore, however whoever conducted the preflight here, I assume SO, failed miserably.
I am sure our Boeing rated friends could advise us on why no engine warnings at all appeared? Strange.