Omitting the Particle of Address

Al-Munādā: Vocative Types and Rules

وَقَدْ يُحْذَفُ حَرْفُ النِّدَاءِ لَفْظًا، نَحْوَ: «يُوسُفُ أَعْرِضْ عَنْ هَذَا».
Translation: Sometimes the vocative particle is unspoken, e.g. “Yūsuf, turn away from this”.

This wording occurs in Qurʾān 12:29. The addressee is present although “yā” is not spoken.