From the Air France 447 findings: "Between the autopilot disconnection and the triggering of the STALL 2 warning, numerous messages were displayed on the ECAM.

From the Air France 447 findings: "Between the autopilot disconnection and the triggering of the STALL 2 warning, numerous messages were displayed on the ECAM. None of these messages helped the crew to identify the problem associated with the anomalous airspeed." Knowing merely that you're in alternate law is not sufficient to know the entire consequences of the mode you're in.