Final answer:
David learned about the job interview at the Blouse Barn when Judy Jones approached him and mentioned his absence.
Step-by-step explanation:
David knew about the job interview at the Blouse Barn because Judy Jones, a familiar person, approached him and told him about it.
In the passage, it mentions that she smiled at him and said, "When did you get back?" This implies that she had information about his absence and the interview.
The specific details of how David knew about the job interview are not provided in the given passage.