Where's God? He just went by you

The unsaved person does not perceive God because of his sins. The sinner's sins have separated him from God. God though, truly exists and is there. He goes by the unsaved man, as it were, and His presence is not detected. The following Scripture tells us this very thing:

Job 9:10 Which doeth great things past finding out; yea, and wonders without number.

11 Lo, he goeth by me, and I see him not: he passeth on also, but I perceive him not.

Since God is operating in an entirely different realm of existence (the spiritual), those limited to another realm altogether (the physical) cannot perceive His reality. God can only be rightly perceived by someone if He allows that person to perceive Him through the eyes of faith – which only He can give.

Hebrews 11:1 Now faith is the substance of things hoped for, the evidence of things not seen.

Faith is a gift of God to certain ones (the elect) who are then able to see Him (seeing in the sense of knowing His existence is certain) who is Himself otherwise invisible:

Hebrews 11:27 By faith he forsook Egypt, not fearing the wrath of the king: for he endured, as seeing him who is invisible.