I never said it was?
I'll be a little less lazy: A = God caused this event, ("God works in mysterious ways")
There is no evidence against "God caused this event,"
Therefore, "God caused this event."
It doesn't matter if you didn't actually phrase it as an argument, saying that God works in mysterious ways is making claims, claims which are illogical. Not putting something in the form of an argument, doesn't mean arguments aren't be presented, or that you can't say some illogical, fallacious, etc.