A lot of social actions aren't available while they are working, and many work hours they aren't supposed to. They also work from many places on the map. I found Hiro at Sako's multiple times, but he would act as if he was at work. Sebastian also worked on Sundays and sometimes would just disappear from the building.

The social interactions are currently meant to be available only outside of work hours. The "work" mechanic is currently a placeholder for how it will be fully implemented so the NPCs tied to whatever shop or service, regardless of location, can provide their service if it's within their scheduled working hours. Also NPCs "disappearing" should be fixed now for the most part.