What happened during Dev's Udyapan ceremony that made him think Sai Baba broke his promise?

During Dev's Udyapan ceremony, he invited Sai Baba, who promised to attend. As detailed in Chapter 40, a Sanyasi arrived first alone, and then returned at noon with two other companions for the meal. Dev served them well but failed to recognize the Sanyasi as Baba, thinking he was just an uninvited guest. Because Dev was expecting Baba to appear in a more recognizable form, he believed Baba had not kept his word. He expressed this disappointment in a letter to Jog, stating he felt deceived and that Baba's promise had turned out to be false, completely missing that Baba had fulfilled his promise in disguise.