Visible crew/equipment: When Harm and Webb walk into Harm's apartment talking about Harm's brother, a crew member can be seen.
Visible crew/equipment: When Rabb and Bud meet Elaine on the beach a boom Mic is visible.
Continuity mistake: Just before Kate asks Rabb if he was a pilot she starts to take a drink from her cup. The shot changes she starts to take a drink again. (00:38:30)
Answer: Officially, the individual has been ordered to attend, failing to could be interpreted as either, Failure to follow orders, dereliction of duty, going AWOL, or even desertion. It would depend on the underlying reason as to why the person doesn't appear.