I agree...
a series of technical errors and errors in judgement most likely led to this.
This has happened one other time that was posted on the forums that I am aware of. The final findings were the c clip was installed in the wrong direction and worked out of it's recess due to use. Most external c clips have a slightly beveled edge and a sharp edge. The beveled edge makes for easier instertion. The sharp edge needs to face away from the forces that would unseat it. So the sharp edge should face out towards the lowers in the case of reassembling the RS damper rod or air piston rods. Unless RS has changed their c clips recently this should hold true for current forks.
Fortunately in the first instance of this reported on the forums, the rider said WTF!?!? when the damping went away, stopped riding, and went home to figure it out.
Unfortunately in the current case the rider ignored the warnnings and paid for it.
Good Dirt