On iPhone 5 (possible all iPhones?) using point lights with Non-baked affect AND Shadows enabled will cause all the models to disappear. If either the Non-baked or Shadows setting is disabled, the models in the scene will appear properly again.
I’ve tested this in both Safari and Chrome; the bug exists on both.
It doesn’t seem to matter if other lights exist in the scene; a single point light with those settings enabled will break the scene.
Here is an example (the starter model viewer project–the only change is that I changed the light from a directional light to a point light).