The in-house PR leader consulted the guest directory for the name of the firm and told me later, "I would never hire that agency".
Does that send chills up your spine? It should, if you are in an agency. Reputation is built on demonstrating good judgment, among other things. This team clearly underestimated the caliber of the crowd, and how noticeable their exit would be. As a result, their card is forever marked in the eyes of an influential communicator.
Of course, there are sometimes good reasons for some people to duck out of events. But there are ways of doing things correctly, and serious consideration needs to be given to the environment and decorum of a given situation. Clients and prospects are everywhere, and they do care about what you do.