How do I answer someone who says God was not there for him when he suffered some trauma?
God is our creator, and so he is the source of everything we have and everything we experience. We tend not to think of God when things are going well and to remember him only when things are going painfully. He is also—and indeed, most of all—a person. What would you think if someone took all the good things you gave, as though you were not there, and then when that person noticed anything missing he began to blame you and claim that you didn't care for him?
The fact is that God has given us everything—our being itself (we would be literally nothing without him), our powers of soul and body (no movement, no pleasure without him), our possessions, and everything and everyone else. So when we experience lasting trauma, we need to focus our attention on all the good things that still surround us, which God has given us, and not only on the pain or loss we have suffered.
Even so, God surely desires to give us some additional gift that we would not have had had we not had the trauma. "Sadder but wiser" is an old expression, but it says a lot. Only with trials and crosses can we enter the kingdom of God. Jesus looks on us with great love when we suffer the effects of trauma, for who understands it better than he, who took upon himself the sins of the world? In fact, God is closer to us in our trauma than he is in other happier experiences.