What's the story about Kaka Mahajani's friend who didn't believe in idol worship and his visit to Shirdi?

This story involves a friend of Kaka Mahajani who was a devotee of the formless and averse to idol worship. As detailed in Chapter 35, he agreed to visit Shirdi with Kaka only on two conditions: he would not bow his head to Sai Baba, nor would he offer any Dakshina. However, upon arriving at the mosque, Baba spoke to him in a voice that was a perfect imitation of his deceased father's. This profoundly moved the friend, causing him to forget his resolve and bow at Baba's feet. Later, Baba asked Kaka for Dakshina twice but never asked the friend, which left the friend feeling restless.