Or do we retroactively place our current theology of God on God?
Consider the Garden of Eden: '[T]he Lord God called to the man, and said to him, “Where are you?”' (Gen. 3:8-10)
Now today we make it into a rhetorical question, but was this always so? In this story, God is spoken of almost in a physical-bodily sense as walking in the garden, since "they heard the sound of the Lord God walking in the garden" as he moved about, and then tried to hide themselves from his view!
Next think of the tower of Babel - "The Lord came down to see the city and the tower, which mortals had built" (Gen 11:5) - Did he not just know already? Also this story makes it appear like God is worried about the potential of man (Gen 11:6)!
Then this idea is reinforced some more in the story of Sodom and Gomorrah, when God needs to go and check out their sin to see if the outcry he's heard is accurate!
Then the Lord said, “How great is the outcry against Sodom and Gomorrah and how very grave their sin! I must go down and see whether they have done altogether according to the outcry that has come to me; and if not, I will know.”
This next one may be a stretch, but it comes to mind anyhow: "For the eyes of the Lord range throughout the entire earth" (2 Chron 16:9).
Other translations say God's eyes "roam" or "run to and fro" throughout the earth. Maybe it's just a poetic way of saying "God sees all", but does it mean he sees all simultaneously — as an all-knowing God should/would? Or is this in keeping with the earlier ideas of God having to come down to a location to inspect it fully, that he goes about the whole earth checking out things and people?
Maybe this where Angels play their role; as in, they are all over the Earth reporting back to the Lord about what they see and hear, so that he can act on situations — as messengers not only from God, but also to God?
Then you also have Proverbs 15:3 saying "The eyes of the Lord are in every place, keeping watch on the evil and the good" which does sound similar to the thought behind the Chronicles verse, and so is probably confirms that it is more of a poetic way of expressing what we would now just call "omniscience."
At the moment I can't think of any other places off the top of my head in Scripture where this idea appears to be present. But other Old Testament verses do also come to mind that show the opposite. For example in Psalm 139:1-4:
O Lord, you have searched me and known me.
You know when I sit down and when I rise up;
you discern my thoughts from far away.
You search out my path and my lying down,
and are acquainted with all my ways.
Even before a word is on my tongue,
O Lord, you know it completely.
Along with Job 21:22; Psalm 33:13-15; Psalm 90:8; 1 Chronicles 28:9; the view of God as knowing all we do, say and think becomes more apparent and the earlier passages from Genesis appear not to line up with this picture of God, as they do seem to suggest that God didn't "just know" everything that was happening without having to go and see for himself (although Gen 4:8-9 would give the impression God didn't know something, until you read verse 10).
But then, maybe this was just a limited understanding from the primitive Hebrews perspective on how God works and acts?
Then again, I suppose this would all rest on how "literal" you read it or how in/fallible you see the Bible and some of the earlier stories, and if it says "the Lord said.." then he really did say it verbatim, and therefore God did need to go and check things out for himself in order to know something.
I'm more inclined to think that this could all be brought under the umbrella of progressive revelation again. The New Testament would appear to show God in an all-knowing way completely, without leaving much room for anything but omniscience, for example: Matthew 10:29-30; Matthew 6:3-4; Acts 15:8; 1 Corinthians 4:5; Ephesians 1:1-14; 1 Jn 3:19-20.
I think it's safe to say that most of Scripture confirms God's omniscience. Especially since Jesus spells it out quite clearly that not even birds will die without the Father knowing about it, we can rest assured that God does know and see everything, so then we can feel safe fully trusting him with our lives and our future knowing he will direct our steps faithfully (Proverbs 16:9).