Whilst the nexus describe query parameter will give you a lot of information about why an artifact can not be found there is one vital piece of info that is missing.
In the case of a NOT_FOUND result and that result being in the cache - you have no idea when nexus will check the upstream repository again.
(hit the following URL twice)
result "compass : The path /org/compass-project/compass/0.0.1/compass-0.0.1.pom is still cached as not found for repository M2Repository(id=compass)"
But when that cache expire which is a really important piece of info is not clear.