ESXi issues at Gold

http://tomaskalabis.com/wordpress/how-remove-unmountedinaccessible-datastore-from-esxi-host/

Actually, I don't know why I didn't think to do this anyway, but here's all I did:
Switch to Datastore view
Click on the dead DS, and then on the hosts tab. The hosts that think the DS is still alive will be listed.
Click on each host and tell it to rescan the HBAs, etc.  When they've finished scanning, they'll drop off the list.  Eventually, the DS will disappear.
 
https://docs.vmware.com/en/VMware-vSphere/6.0/com.vmware.vsphere.storage.doc/GUID-ED44059C-CB8C-4B4E-872A-15DABC96D395.html
 
Prerequisites
    Remove or migrate all virtual machines from the datastore.
    Make sure that no other host is accessing the datastore.
    Disable Storage DRS for the datastore.
    Disable Storage I/O control for the datastore.
    Make sure that the datastore is not used for vSphere HA heartbeating