There is no throttle on an Airbus. And the thrust lever position was not relevant in this accident. Basically, the pilots were so startled by a false warning coming out of nowhere that they, in panic, started doing random stuff instead of realising that the aircraft has been cruising with their current settings just fine for a while so the most sensible thing to do would be to calm down, leave the controls alone and take care of the ECAM warnings with the help of their quick reference handbook. Had they done that, the pitot tube icing situation would have most likely resolved itself by the time they finished troubleshooting. It is perfectly possible to fly with unreliable airspeed, there are procedures for that which basically amount to "set the thrust in a specific range, keep the wings mostly level with a slight nose up position and you'll be fine".