Autobrakes on landing: Applied when both throttles at idle and wheels spun up.
Autobrakes on RTO (rejected takeoff): Maximum braking with both throttles at idle, speed above 85 kts and wheels spun up.
Me: below 85 the autobrakes go to low brake or go off.
Speedbrakes on landing; required by checklist (the study guide is from Delta but probably the same procedure as American)
Extend when wheels on ground and throttles at idle.
My speculation: When the thrust reverser did not deploy the landing pilot may have pushed the piggybacks back to the stowed position and inadvertently pushed one or both throttles slightly above idle, pulled the throttles back to idle then redeployed the T/R. But in doing so the autobrakes and speedbrakes would have been unarmed (dis-armed?).
Or, on an icy runway they did not get wheel spin up as quick as normal.
FAR 121 requires the computed full stop landing distance to be no more than 60% of the runway length. Wet or slippery conditions require the runway length to be no less than 115% of the above calculation. (hows that for paraphrasing?)
You guys are correct, Part 25 jet airplanes do not use thrust reverse in the calculations. Brakes are by far the most effective at stopping the airplane.