Despite the increasing interest in trust in human-robot interaction (HRI), there is still relatively little exploration of trust as a social construct in HRI. We propose that integration of useful models of human-human trust from psychology, highlight a potentially overlooked aspect of trust in HRI: a robot's apparent trustworthiness may indirectly relate to the user's relationship with, and opinion of, the individual or organisation deploying the robot. Our Social Triad for HRI model (User, Robot, Deployer), identifies areas for consideration in co-creating trustworthy robotics.