I have a number of devices that we have deleted from Solarwinds for monitoring/polling and I still occasionally see alerts for them in the "Last 25 Events" window saying they are unreachable. I've searched the database backend and searched with the Orion web gui and can't find any existence of these hosts any more. These usually show up after the polling servers are rebooted. It's like they are in a cache file local to the polling engine. Is there a file I can clear out that maybe retaining some of these events?
Doesn't sound like a known issue unfortunately. A support ticket may be the way to go.