What term refers to someone who missed their train, as mentioned in the conversation?

The term that best refers to someone who missed their train is "late." This term effectively communicates that the person was not on time for their scheduled departure. In the context of trains, being "late" implies a failure to catch the train due to arriving after it has already departed.

While "passenger" and "commuter" are related to individuals who travel by train, they do not specify the circumstance of having missed the train. A passenger is anyone who is traveling, and a commuter typically refers to someone who travels regularly between home and work. On the other hand, "absent" generally conveys a broader absence from a place or event, and is not specifically tied to train schedules. Thus, "late" directly addresses the situation of having missed the train, making it the most suitable choice.