I think every VM admin has experienced the following situation; For some reason planned or unplanned your vCenter server is down, no real issue because it will not affect the VM's running in your vSphere environment. Even HA will continue to work.
But how do you know where a specific VM is located (on which host) when you don't have vCenter ?
I already had a small script which allowed me to search for a VM on a selection of hosts or all active hosts of a environment, because if you vCenter is down unplanned their might be some other servers / VM's that are also down with the same root cause. If this is the case you will not only have to worry about getting your vCenter back up-and-running but you will also get a lot of questions on how to find and access other unresponsive VM's. This will be a challenge for any Admin which solely relies on the vSphere (web) client, because this Admin will have manually and separately logon to every host with his vSphere (web) client and search the inventory per host to find the VM he is looking for.
This is not a big problem if the environment has 5 or 6 hosts but the problem gets bigger as the environment gets bigger, just imagine the amount of work and time it will take when you have to search thru 50 hosts !.
I had a "vCenter down" situation recently with a customer and some other VM's became unresponsive. These VM's did not respond to RDP and because vCenter was down there was no direct way to know on which of the 58 hosts ! the VM's were running. So I got my old small script to lookup some of these VM's and one of the Admins saw this and he asked if he could also run it to find some VM's. This Admin had little experience with vSphere so he had some trouble to provide the needed input into the script before it would work (ESXi hosts IP or DNS to connect to and name of the VM which it was registered with in vSphere) but with a little help he managed.
After this event I thought I would simplify the script by using pre-created files with host information of the vSphere environment and have a selection menu to choose from, the only info that you need to provide is the full name of the VM.
Of course you will need to create the files, but you can do this when vCenter is up and it is easy to retrieve this kind of information.
The files you need to create are one file per search selection, in my script I have 1 file for every Cluster and 1 file for the complete environment. The file is a plain text file with 1host IP address or DNS name per line.
For me this is a script (with or without the menu) that you want to have available to you in case of a emergency, it take little time to setup and will help you big time in case of a issue.