"And they have built the high places of Topheth, which is in the valley of the son of Hinnom, to burn their sons and their daughters in the fire, which I did not command, and it did not come into My mind," (Jer. 7:31).
Is the Lord actually saying that He did not think of something? Even in open theism, God knows all things actual as well as potential. That means God can know all things in the present tense as well as all possibilities of things that could exist. Certainly God who knew the past sins of Israel would have thought about them doing such sin -- as horrible as it was. So, it doesn't make sense to interpret this as God admitting that He never thought of something.
Furthermore, the NASB,1 NIV, RSV, 1901 ASV, translate this as "and it did not come into My mind," where the KJV, and NKJV translate it as "and it did not come into my heart." What is interesting is that the LXX2 uses the Greek word kardia, "heart," instead of the Greek word for mind. Since we can conclude that God can contemplate all potential forms of rebellion, we can then also conclude that God is addressing the issue of human moral behavior instead of expressing ignorance since that is what God is talking about. In other words, their sin did not enter the intention of God's heart in His plans for Judah.