Acharya Prashant explains that when a physical teacher is not present, one should seek refuge in the 'Sangha' or the community that preserves and spreads the teacher's message. If even the Sangha is unavailable, one must rely on the inherent righteousness within their own heart. He emphasizes that while the physical form of a teacher is temporary, their teachings are abundantly available through books and recordings. He urges seekers to take advantage of the opportunity to learn while the teacher is still physically present, as the physical body is unpredictable.