If you found pieces of timing chain guide rails...
And your rocker came off...

Chances are (unfortunately) that a failed timing chain guide ($20 plastic part) caused your engine failure. The timing chain jumps time, and the valve smashes against the piston (which would result in the rocker arm being thrown off). Usually you need new valves and guides for an entire side of the engine, often it damages the valve seats and pistons as well. At this point what you need to do is verify whether or not you can turn the engine by hand. Don't attempt to use the starter, it'll spin the engine too fast and cause certain damage if the chain has jumped time but no serious valve/piston meeting has occurred yet.

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Back in the saddle - 1972 280SE 4.5