Am I right in thinking that -10,000 ft/min is around 100kts down? In which case if their airspeed was <60kts a normal attitude would produce a very high AoA.
If so they may have a normal attitude displayed, unknown airspeed indication, and no stall warning. Perhaps only clue was high rate of descent which they might not have believed given normal attitude?
It's not clear if there was no stall warning while the aircraft descended. The BAE report only states that the stall warning was suppressed when they reached the peak of their climb, when the measured speed dropped below 60 kts, but started up again as the aircraft began to fall. The report does not say if the alarm stayed on or shut off.
The last recorded information was that they were moving at 107 kts ground speed, so depending on what direction the wind was blowing, they might have had sufficient forward speed for the stall warning to continue sounding for the entire descent.