First of all Welcome to the QB! How long ago did you heat it? Usually rubber needs to be cooled off completely so it is not tacky. In this instance I would put the quilt in the freezer for a few hours and see if this helps. For future reference you should use a sturdy bayberry cloth or light towel over t shirts when pressing. Or on the ironing board if applying your interfacing on to the back.
I am not sure that putting it in the freezer then letting it thaw will take care of the problem but the complete cooling should help. Maybe someone here will have a better idea. And yes you did it right, posting that is. Welcome aboard.