The Father cannot be seen by humans as no one can see Him and live.
I take it you reject the doctrine of omnipotence then? After all, an omnipotent god would, by definition, be able to show itself to a person without that person automatically dying. Also: is it such a fine thing to come right out and admit that your god, like Medusa or Cthulhu, is inherently inimical to human life?
The Son did Show up but we killed Him.
Whaddaya mean "we?" Also: again, omnipotence. If "the Son" didn't want to be killed, would humans have been able to kill him? If he did
want to be killed, would humans have been able to avoid killing him? Go read the Last Supper story in the Gospel of John where Jesus and Satan tag-team Judas and force him to "betray" Jesus.
The Spirit cannot be seen as he is a Spirit.
What other things are there that "the Spirit" cannot
do? Lift a paperclip? Generate a little static electricity? Just how weak is "the Spirit," anyway?
But....We will see Him face to face, for now we see through a glass darkly but all will be revealed in the eschcaton.
You mean, after you just went and told us that seeing him is impossible? You're going to have to do better than that.