The Father has willed that He be known through His Son.
"If you have known Me, you know My Father also." - John 14:7
"Believe Me that I am in the Father and the Father is in Me." - John 14:11
It is Christ who comes to Abraham.
It is Christ who speaks through the burning bush to Moses.
It is Christ who is with the Israelites in the wilderness.
"Truly, truly, I say to you, before Abraham was, I AM." - John 8:58
"For I do not want you to be unaware, brothers, that our fathers were all under the cloud, and all passed through the sea, and all were baptized into Moses in the cloud and the sea, and all ate the same spiritual food, and all drank the same spiritual drink. For they drank from the spiritual Rock that followed them, and the Rock was Christ." - 1 Corinthians 10:1-4
Christ is present throughout the Old Testament. Who does Jacob wrestle with? An angel or the LORD? Yes, says Scripture. And Who is that? It is the very Eternal Son and Word Himself, Jesus Christ.
It isn't Christ instead of the Father or to the exclusion of the Spirit, of course; because of the Perichoresis of the Three Persons. But most certainly it is Christ right there, everywhere, throughout the pages of the Old Testament.
The Father, Christ the Son, and the Holy Spirit--everywhere.
So I don't understand it when you say that we clearly can see the Father and the Holy Spirit, but not the Son.
Because it is the Son that we meet at every step of the way through the entire unfolding drama of redemption in the Bible. And it is He who becomes flesh in the womb of the Blessed Virgin.
-CryptoLutheran