Silly Muslim,Quite hilarious!
It would have been shirk only if someone had said "Muhammad was the son of God" or "God's partner" or "God beside God".
In the Shahada, the person declares that there is only one God and that Muhammad was a messenger of God.
Wasn't I right when I had suggested earlier that you should go back to school?
JEWS declare that there is only one God, named YHWH, but they categorically REJECT Mohammad as a false prophet, which means that they aren't MUSLIMS at all, and will go to ISLAMIC HELL when they die because of this REJECTION of Allah's bona fide partner. Isn't that right?