Final answer:
The show 'The Office' does not explicitly reveal who leaked to David Wallace about Andy's absence. The environment of the office is such that information spreads organically, so it's likely the news of Andy being away might have come out through natural office conversations.
Step-by-step explanation:
The student's question is about the character Andy from the television series The Office, a popular American mockumentary sitcom. In the storyline, it is not explicitly stated who leaks to David Wallace that Andy was away from the office for 3 months. However, it can be inferred from episodes of the series that the information may have naturally come out due to the changes and events occurring in the office during Andy's absence.
In looking at the details provided, none directly answer the main question regarding Andy's absence; however, the last two provided snippets provide context for Andy's behavior which may be indirectly related to his future absence and the subsequent leak of this information.
To address the student's question, while the show does not definitively reveal who told David Wallace about Andy's absence, it is strong evidence about the open and often gossipy environment of the office, suggesting that the news could have spread organically through the office staff.