Looks like he was shining the flashlight on the pitot tube during the walk around.
Either did not notice(make sure to look and actually observe) or perhaps noticed and then forgot.
Seeing as I am always looking for solutions based on the reality of events occurring(instead of discussing penny pinching), I suggest, as a general rule, having a policy of stopping the walk around when an issue like this is discovered, advise maintenance, and then resume the walk around. It makes it less likely that the issue will get forgotten.