Do they exist and were are they found?
Examples?

First one comes to mind is in Genesis, In the beginning God created the heavens and the Earth , Cliffnotes version here, but the Trinity has always been, even before creation. So God created, but before He brought forth the land, Genesis 1:2-“the earth was without form…and the spirit of God was hovering over the face of the waters. Ok, so we’ve got God and the Holy Spirit accounted for. Where’s Jesus? We have to turn to John 1:1, “In the beginning was the word and the word was with God. He was in the beginning with God.” If we turn to John 1:14, “and the word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son, from the Father, full of grace and truth.” The trinity was in place since the beginning. I know you said Old Testament and I used some New Testament to verify it but that’s how the Scripture works.

Genesis 3:22

Genesis 1:26

Then God said, “Let Us make man in Our image, according to Our likeness; let them have dominion over the fish of the sea, over the birds of the air, and over the cattle, over all the earth and over every creeping thing that creeps on the earth.”

The man has become as one of us. ( yes)

There alot of things God did not tell us because we could not understand it.

Yes Gus there are many mysteries in the bible. Prophecy that had not been fulfilled.
Though the old testament is full of appearances of the Godhead.
Visions , God in the cloud. The angle of the lord , Jacob wrestling with him.
Joshua speaking with a man on Holy ground after crossing the Jordan. Abraham feeding the Lord and the Angels
the fatted calf.
And so on.