Mosiah 16:4

"Thus all mankind were lost; and behold, they would have been endlessly lost were it not that God redeemed his people from their lost and fallen state."

When Adam fell from the garden of Eden man became lost and fallen, meaning that they were no longer in the presence of God.  With Christ's atonement, He made it possible to enter into God's presence again. Because of the Fall, Christ came to redeem us from that fall. We are not lost!