Final answer:
The message left on the answering machine is missing complete information such as the specific time and location for dinner, making it the absent characteristic of useful information in this scenario.
Step-by-step explanation:
In the given situation, where a message was left on an answering machine proposing dinner, the aspect of useful information that is absent is Complete. The message does contain information that is relevant, understandable, and it seems to be delivered in a timely manner. However, it is not complete because it lacks details such as the specific time for the dinner, the location, or even a way to get back in touch if Bob does not have the caller's current contact information. Information completeness is crucial for effective communication and decision-making, much like having complete information about products or services as in seeing the apples or knowing the local reputation of the restaurant helps in making informed choices.