Aren’t some representations exactly what they would look like to us if one did appear? We’re not gonna see it in 4D but we’ll see the 3D representation of it being pushed through our space. Like in Flatland, the sphere pushed through 2D would be a point that grows as a circle, shrinks back down to a point, then disappears. They’ll never see a sphere and can’t imagine a sphere, but they would see the 2D representations of it.