Maybe somebody (Hottie? or maybe even Bua-ji) will let slip to him how Kaajjal was in coma and he may suddenly click that this is the same girl that Dev loves "the hospital wali".
Since I have taken an active dislike for Dhruv I am trying to imagine scenarios where Dev need not waste his energy explaining everything to this Big Nut that thinks its in love with a girl with whom he has not even exchanged more than 25 decent words in total!