Took me awhile to track this down. I was trying to clear up the yellow icons on my main EOC page and came across a device that was not showing up in the EOC mapmaker. I found an icon that was gray on one of my EOC nested maps. It said it was a missing node. I then looked and sure enough it was not in the EOC list of devices under that Orion server. Further research showed it was unmanaged on the host Orion server.
How does EOC handle unmanaged nodes - just ignore them?