Looking at the picture that cover is hardly what I'd call signal yellow. I can imagine that on a dull day, at the end of a long shift, your brain could play some funny tricks with you causing you not to see them.

It boggles my mind they wouldn't have put some kind of NFC chips in it at least to chime an alert "check intake cover".

It also is truly strange it couldn't detect the airflow anomaly on spool up, and at least alert the pilot / launch officers.

Could have a pattern embedded for super easy image recognition and a simple computer running continuous recognition of aircraft taking off (I'm sure there's cctv)... There's just so many ways to help prevent such a mistake!

I don't envy the crew explaining this.