Why did Jog ask Deo about a black dog when he saw him in Shirdi?

There is a misunderstanding in the premise of this question. The provided text from Chapter 41 clearly states that when Jog met Deo in Shirdi, he asked him, 'Why aren't you reading Dnyaneshwari daily these days?' Jog's question was about Deo's well-known spiritual desire, not about a black dog. The chapter does not mention a black dog at all. The narrative focuses on Deo's long-standing but unfulfilled wish to study the Dnyaneshwari, his various failed attempts, and his eventual decision to wait for a direct command from Sai Baba before starting the practice.