The text says Sai Baba left his body. Does this mean he is gone forever?

No, according to the perspective offered in the holy book. Chapter 43 strongly argues that Sai Baba is not gone. It states that his body was merely an adjunct and that saying he 'left the body' is a limited understanding. The text explains that he burned his body in the fire of Yoga and merged himself into the unmanifest, continuing to reside in the hearts of his devotees. It poses the rhetorical question, 'he who was filled with consciousness and was firmly imprinted in the hearts of devotees—can that body be said to have perished?' The author concludes that his mind does not accept this idea, reinforcing Baba's eternal presence.