Canceling a Connection on an Added but Disconnected Host Removes That Host from VirtualCenter
Details
Why was my disconnected host removed from VirtualCenter?
Solution
The process of connecting a host treats a command to cancel a
connection as a command to cancel adding a host. Therefore, the
disconnected host is removed.
If this happens, re-add the host.
To correct this, upgrade to VirtualCenter version 1.3.1 or
later.