You can talk to your big boss about work process, not about what the guy did
. You can say that the guy did a good job. However, since there is no
formal process or procedure to follow so that integration can not be
guaranteed. This may cause big issue later on. Before you talk to your
boss, try to make up a procedure yourself to make the guy report to you or
at least let you review his work to make sure it fits in the whole project.
Don't complain about the guy and don't get into politics. Just emphasize
from the management side and show your boss how the procedure will help the
company.