Apple has officially clarified what happened on stage when the first demo of Face ID didn't go as planned.
Here's what an Apple rep said about the debacle: "People were handling the device for stage demo ahead of time," says a rep, "and didn't realize Face ID was trying to authenticate their face. After failing a number of times, because they weren't Craig, the iPhone did what it was designed to do, which was to require his passcode."
On stage, when Federighi tried to authenticate his face and it didn't work, he quickly switched to the second demo device and everything ran smoothly from there on out.
Much like with Touch ID, when Face ID is unable to authenticate via face recognition, it will prompt for a passcode before attempting to recognize a face again