They can't defend their theology because it is inconsistant with Christian thought and is no theology whatsover.
In fact, I have an idea that there are no accepted Mormon theologians given recognizence anywhere in Christian theological realms unless you know of some? I would be happy to read them if there are any.
One other verse that proves that Christ's church was never lost and "re-found" is Psalm 102:12
But thou, O LORD, shalt endure for ever; and thy remembrance unto all generations