To be honest, it probably wasn't the case. If the phone had landed on the concrete of a parking lot I don't think any case would have prevented RUD. The phone came down in a shrubby area with soft ground, which helped cushion the fall.

the aerodynamic character of a phone in free fall should enter into it as well.

Slate has an article discussing this with a physicist, who calculated that the phone would reach terminal velocity of 60 mph (96 km/h) at just over 300 feet (100 meters).