Vmware Instance or ESX Server table field "install_status" is changed from "Installed", or any other value, to "Retired". The install_status is update is not reflected in the Audit History.
From VCenterDatacentersSensor script include:
// Mark stale VMs as 'retired'
gr = new GlideMultipleUpdate('cmdb_ci_vmware_instance');
gr.addQuery('object_id', 'NOT IN', vmObjIds);
// Mark stale ESX servers as 'retired'
esxGr = new GlideMultipleUpdate('cmdb_ci_esx_server');
esxGr.addQuery('object_id', 'NOT IN', output.hosts);
esxGr.setValue('install_status', '7'); //Retired = 7
The VCenterDatacentersSensor script include can be updated to avoid the CIs being marked as retired. Customized script includes are not updated on upgrades and would be owned by the team which updated the script. In this case, it is best to leave the script OOB as this is expected behavior.