You may be ignorant of His presence at the time, but that doesn't mean He doesn't exist. If you look, you will find that He was there all along. You can know that God exists.
God is not subject to the dimension of time. He dwells in eternity.
I cannot express to you how grateful I am that I am a Christian. Before I was a Christian, I went through a time in my life where I just didn't know why I was alive.