Before he left infinity ward, he said a quick good bye to the treyarch team too, but it dint stop him by switching the file to other zombie map ideas!!
Proof:
There is a bowling room in tranzit, ( his name bowling)
There is a chinese map, where his gf comes from (shes chinese)
The prison of mob of the dead is a sign where he activision belong for ruining mw3
ALL THE PUZZLE ARE IN WAKE UP!!!