I played a BA today against duelmaster and had hysteric sign on the field [after activation] and he destroyed it during his turn, and the effect didnt work, and i had plenty of "Harpie" monsters left in my deck, this isnt the first time it happens but this for sure was a bug
replay - http://www.sendspace.com/file/6fglw0

and if it wasnt, tell me why it didnt work cuz i need to know xD