I was able to get away with carrying a knife through the Shanghai metro, and onto the maglev to the airport. At entries to both, they x-rayed my bag and were not enthused by the knife's presence (one guard made vigorous stabbing gestures to communicate his concern). But it did not take much to assure them it was a souvenir not to be used as a weapon.

My point is perhaps you were profiled to your benefit as well.

Edit: I'm from the US.