.....then just say the pilot changed the trust levers position to idle...
For SA Airbus, if you bounce after touchdown with the throttles above idle, if the levers are then pulled back within 3 secs of touchdown, the ground spoilers will deploy in the air and the plane will drop hard.
According to Airbus, main causes for hard landings:
35% Late / weak flare
23% External Perturbations
20% Nose down orders
17% Retard during bounce*
5% Dual input
*17% of the 82 Hard Landings 1998-2008 were due to retarding of levers after bounce. That 17% accounted for 40% of total L/G replacements.)