Ihave seen ice placed on the head of a glow engine before and that had no effect on how it ran but that was in a test mount, it melted it rapidly whereas the Diesel did not do so as fast - but bothe kept on running .
So I am wondering here was it just the 'coolng effect' of the weather or water being ingested into the engine that actually caused the missing?

As I am struggling to see how a shower could cause a miss in the engine if nothing else came into play.

But honestly I am just summizing here.