Sociology has a long history of analyzing relationships between strangers in everyday life. The ubiquity of social media and mobile technologies, however, necessitates refined theories of how people relate to and interact with strangers in a social world where online and offline contexts are intertwined. This study examines public encounters between acquainted strangers, a type of connection fostered through social media wherein people are both digital acquaintances and offline strangers. Drawing on ethnographic data of queer men who use mobile dating and hookup apps, I find that queer men experience these encounters as routine yet problematic, which past theories of stranger relationships cannot fully explain. I argue that offline interactions with acquainted strangers amplify interactional uncertainties around identification (e.g. "I know them, but do they know me?") and recognition (e.g. "What are the moral demands of our relationship?"). Managing these uncertainties is socially significant as the decision to regard or ignore an acquainted stranger marks not only interpersonal acceptance/rejection but also broader forms of belonging and exclusion. These findings underscore how mobile technologies are fundamentally transforming what it means to be a "stranger."