I really enjoyed Crysis 3 so far, but why is there no Alpha Ceph?????

I heard of the Invinciblebug, but after I jump into the beam, there is no boss! He seems to be stuck on that giant beamthing. Did I forgot something (press a button) or is this a bug?

I can ran around, hack the turrets, enter the tankcannon etc. but there ist no boss.

I played the complete level again, but still no boss around.