In a frame of snooker, the scores are level and only the Pink, Black and cue-ball are left on the table. The Pink is hanging over one pocket and the Black is hanging over another. Player A pots the Pink and the referee calls 'Six' and everything is perfectly correct. However Play A loses the frame without making a foul on the black. How does this happen? Could any body explain? (Black is just right at the edge of the pocket)