I need to configure Splunk Enterprise using the reporting and notification tools to create a report with notification of the following events:
Loss of communication with hosts and devices
Logs no longer being collected.
How would I go about crafting a search for these requirements?
Finding something that is not there is not Splunk's strong suit. See this blog entry for a good write-up on it.
https://www.duanewaddle.com/proving-a-negative/
There are apps that can help, however. Check splunkbase for TrackMe and Meta Woot!