Don't shoot the piano player
I've been thinking about this for a while now that I'm listening to the cast I had to weigh in. I think the reason the Man in Black new the maze image was in Kissy's scalp is the old unwritten western gun fight rule that you don't shoot the Piano player. Out of all the hosts, he's the least likely to have had his scalp replaced and that's why the MIB thought it might be there.
Additionally, I don't think the Maze image existed in the park until the MIB started flashing it around. The image is now being recreated by the hosts and it's spreading around. This explains why Ford is acting like he's reacting to the image for the first time.
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I also think that the host started to carve the maze symbols all over the place after MiB started on his path.