The p-zombie thought experiment pre-supposes or rather, defines, consciousness as being non-physical. If it were physical, the two worlds would obviously be distinguishable. My take-away from it is that the p-zombie world is simply our world. The theory that "a non-physical consciousness exists" can't be tested and is therefore a bad theory.
The answer is that one of these things is true: * P-zombies would write IDENTICAL papers about how they experience qualia but p-zombie land wouldn't * The mind has some effect on the universe you can detect, so P-zombie universe looks quite different