If you look at fluid in a pipe, the fluid immediatly adjacent to the pipe wall will not be moving and the fluid in the center will be moving the fastest. That stationary layer next to the wall forms a sort of an insulating barrier. Detonation is usually detected by a rise in cylinder head temperature or CHT (many aircraft measure this by a thermocouple in the shape of a washer in place of the spark plug's gasket). Some speculate that this spike in CHT is a result of the explosive ignition of fuel (detonation) disrupting this boundry layer. With the hot gasses closer to the combustion chamber, greater rates of heat transfer occur and the CHT's rise. What I'm getting at is maybe the detonation caused an increase of heat transfer to the exhaust valves which caused the valves to expand and stick in their guides. Judging by the way the rocker arm tore away from its base, I would say there was a stuck valve. It could be that a overheated/stuck valve was causing the engine to run poorly and you misinterpereted it as detonation. Were all of the damaged components on exhaust valves?

This all seems too weird and I want to know what happened. I'm just throwing out everything that runs though my head right now.