So unfortunately I am much less familiar with Maxwell than HFSS. I can suggest some things that might be worth looking into. Look at the vector field for the surface current and it might be there forming loops, but experiencing destructive interference which is why it is not showing up on the magnitude plot. I also am not familiar with the theory and mathematics for eddy currents, so my intuition is perhaps wrong. What material is the plate? Try meshing just the surface. HFSS will calculate the skin depth and include skin losses automatically so you can get away without seeding inside the conductor. Hope this helps, I can always come up with more suggestions.