That idea is mentioned at the beginning of the 1975 movie "Three Days of the Condor" starring Robert Redford...
I’m familiar with the ice bullet concept, but the only ‘not a trace’ would be a lack of a slug, not a cause of death. If it kills you, there is a trace. A natural occurring substance, adrenaline, acetylcholine, can all be used ‘without a trace’ if the autopsy is less than thorough.
Death by impact always leaves a trace whether the impact producer is found or not.