As a result, we adjusted the deliverables on a proposal we were preparing. I tried to find someone by asking people around the office if they knew where she was. At the end of the day, I grabbed a ride to the subway with a colleague who I saw walking by my door with her coat on. We talked shop on the way. This rich communication happened as a natural consequence of being geographically close to his fellow workers.
Information is exchanged, tasks assumed, reports given, action items check-off, etc. etc.
Just because it lasted 30-seconds, doesn't mean that the meeting wasn't important. This person's workplace, as yours, has a rich social ecology which serves to support the activities of the people working there. The interaction of people and artifacts is part of a complex system in which each of us have developed expertise over a lifetime of living in the everyday world. When we separate workers geographically, by moving them to different parts of the building, city or country, we significantly change the social ecology of their workplace. People are no longer aware of each others presence, their current activities, their knowledge of work-related issues.