I came across the following scripture in my studies for this lesson.
D&C 84:19-22

And this greater priesthood administereth the gospel and holdeth the key of the mysteries of the kingdom, even the key of the knowledge of God. Therefore, in the ordinances thereof, the power of godliness is manifest. And without the ordinances thereof, and the authority of the priesthood, the power of godliness is not manifest unto men in the flesh; For without this no man can see the face of God, even the Father, and live.

There has been discussion on this forum that ordinances of the Priesthood are only there to prepare people to receive the higher covenant and that it is possible to bypass these ordinances and see the face of God the Father without such ordinances as Baptism. These verses seem quite clear in declaring we cannot bypass these ordinances. The only possible way through this is to say the power of godliness may be made manifest unto men in the Spirit. If so, how did Joseph see God the Father and God the Son without the Priesthood being first restored?