conspicuous by (one's)/its absence

Especially noticeable by being missing or absent (from something). You're the loudest one in the class, so of course you're conspicuous by your absence! The governor's economic stimulus plan was conspicuous by its absence during his speech this afternoon. A: "How could you tell that I didn't add cinnamon this time?" B: "Well, it's a flavor that's pretty conspicuous by its absence."

Cliché noticeably absent (from an event). (*Typically: be ~; made ~.) How could the bride's father miss the wedding? He was certainly conspicuous by his absence.

Also, conspicuous by one's absence. Glaringly obvious by the fact of not being there. For example, One agenda item concerning publicity is conspicuous by its absence, or The bride's father was conspicuous by his absence. The idea is ancient; it was expressed by the Roman writer Tacitus, concerning the absence of Junia's brother and husband at her funeral procession. [Mid-1800s]

If someone or something is conspicuous by their absence, people notice that they are not there. He played no part in the game and was conspicuous by his absence at the post-match celebrations. Mathematics and science were conspicuous by their absence at the university.

Noticeable by the very fact of not being there. The idea was expressed very early on by the Roman historian Tacitus, in recording the absence of Junia’s brother, Brutus, and her husband, Cassius, at her funeral procession. The phrase became popular in the nineteenth century, and continued to be applied often to political matters, such as the absence of certain provisions in a law, or the absence of political leaders on certain important occasions.

Very obvious through nonattendance. This oxymoron, which goes back to ancient Rome, applies to people or objects that attracted attention because they were expected to be present but weren't. An example would be a close relative who either wasn't invited or chose not to attend a family function. Some literary commentators contend that the phrase has become a cliché, but it's now used so rarely, you may—although at your peril—claim its wit to be your own.