Yes, it should all be in one piece (both flywheel cheeks with the sprocket in the centre. It looks like your outer flywheel cheek has been machined down -ts smaller than a sherpa which has both cheeks the same diameter - I may be wrong as ive never worked on an Alpina. It also looks like they tried to balance it - see the holes drilled in it. Suggests they knew what they were doing.
I'd just get another one - reasonably easy to find..