I followed his receding figure with my eyes until it disappeared into the crowd.
Tips
memory
目 (eye) + 送 (to see off) — literally 'see-off with the eyes,' i.e. you don't physically accompany them, you just watch them go. Strongly emotional in literature, used for partings of parents and children, lovers, the dying.
culture
《目送》 (Watching Them Go) is the title of a famous 2008 essay collection by Taiwanese writer Lóng Yìngtái (龙应台), about parents watching their children grow up and away — anchoring the word's emotional weight in modern literary Chinese.