Conspicuous by one's absence

If someone is conspicuous by his absence (not literarily absent but being unmentioned of his contribution), does that mean he is aware of his absence or does it mean something else?

Hi cooliegirly

When you say something/someone is conspicuous by its/his/her absence, that means that the absence/omission is extremely obvious to people in general.

Amy

His presence or contribution was expected, but didn’t materialise.

Art