This has already happened twice for the same client (windows server on premises CN): SERP server suddenly stops and there is no exe file in the cloudnode folder. We have to copy the exe from the oldver folder and rename in order to be able to start the CN which in turn starts SERP server.
This happend with one of the automatic Cloud Nodes updates in April and yes, correct way to fix it is to copy the executable from oldver folder into cloudnode folder and rename it according to the content of run-cloudnode.sh script.
