The bishop disappeared because it did in fact explode.
When the pawn on c4 captured your pawn on d4, it was capturing "en passant".
Since the piece that was taken was your pawn on d4, your bishop on d5 was taken, according to the rules of atomic chess (your bishop was one square away from the pawn that was taken on d4).
When the pawn on c4 captured your pawn on d4, it was capturing "en passant".
Since the piece that was taken was your pawn on d4, your bishop on d5 was taken, according to the rules of atomic chess (your bishop was one square away from the pawn that was taken on d4).