It's one of the very few arguments atheists advance in support of their view - the hiddeness of God.
But is God hidden? When we make moral judgments we imply there is such a thing as an objective and obligatory standard. When we feel hard done by or complain about injustice, we imply there is such a thing as justice. We intuitively know that there are moral obligations but these obligations demand a transcendent, righteous Being to whom we are accountable. It is evident within us that God exists.
It is evident around us that God exists - the universe we live in, coming into existence out of nothing, balanced on a knife's edge with constants so finely tuned it defies understanding, proclaims the power and intelligence of a Creator. There is no feasible naturalistic explanation.
It is evident to us that God exists - He has revealed Himself in Scripture (the written Word) and in the Son (the incarnate Word). The message of Scripture is unlike any other "holy book". It is a prophetic book, confirming its divine origin. It presents a righteous God who doesn't compromise on justice - only the God of the Bible is "a just God and a Saviour" (Isaiah 45 v 21). The life, death and resurrection of Jesus Christ give evidence that the atheist has to, but can't, deal with. God actually came amongst us.
If someone says, "Yes, but that was 2,000 years ago - He's been in hiding ever since!" It simply isn't true - the written Word is living - it is up-to-date, it is God's full revelation of Himself to man and people can encounter God through it; and the incarnate Word is living - Jesus Christ is alive today, and people can experience the living, life-giving power of Christ when they come to Him in repentance for forgiveness. To the Christian, God is a living, loving, practical, personal reality.
God is not hidden - He has made Himself known to us in so many ways, and we encounter these evidences of the divine everyday. In creation we see His fingerprints; in conscience we recognise His righteousness; in Christ we hear His heartbeat. Paul proclaimed, "He is not far from each one of us" (Acts 17 v 27).
The problem is that man is hiding from God. Adam and Eve did it back in the beginning (Genesis 3 v 8) - they felt guilty and unfit for the presence of God, and so they hid. The human race has been doing the same ever since. Most people can't find God for the same reason a thief can't find a police officer - they don't want to! They know they are condemned by His righteousness, and rather than give themselves up and turn themselves in, they hide in the darkness of atheism or the fog of false religion. The Lord said, "Men loved darkness rather than light" (John 3 v 19), and we naturally hide from the light because it exposes us for what we are. But if we come to the light, and stop hiding from God, there is forgiveness offered, and cleansing avaliable, through the blood of Jesus Christ.
The Lord could have stayed hidden in heaven and left us in the dark, but He loved us too much for that, and He came "to seek and to save that which was lost" (Luke 19 v 10; Luke 15 v 4-7). Don't stay in the dark, step out and come to Christ.