Jesus knew what the scribes were thinking (Matt 9:4). He knows what we’re thinking too. He knows everything. There are no absences in the omniscience of God.
This is not true of any of his creatures – not even the angels, fallen or unfallen. We humans are of massively less intelligence than the angels. Pseudo-Dionysius says that “the intellectual power of the angel shines forth with the clear simplicity of divine concepts.” Their minds are close to God. Meanwhile, we tend to muddy things up.
Still, there are things even angels do not know. There is nothing that God does not know. All knowledge, in fact, comes from God. If you know a thing (and that’s as opposed to thinking that you know a thing), it is because God has given it to you to know. If God did not give the gift of knowledge, you do not know what you think you know. You merely believe it. And mere belief is not knowledge.
Everybody has an opinion. But not everybody has knowledge. The reason angels and men do not know everything is because God has not given us everything to know.
One of the things he does not give us, usually, is the knowledge of one another’s thoughts. People sometimes fall into the trap of thinking that they know what other people are thinking. And this so often leads to judgmentalism. How commonly we fail to give the benefit of the doubt. How commonly we fail to admit our own ignorance to ourselves. We do not know what other people are thinking. We cannot judge them. We do not know their hearts or intentions. But God does.