Create descriptor ESXi 5+

This was tested on ESXi 6.5, but should work from 5 onwards.

The descriptor is basically a text file that contains geometry parameters which point out to the image that actually cotain the data,
usally called "VM0-flat.vmdk".

This is a last resort method when unable to restore the actual descriptor .vmdk file.

1) SSH into your ESXi host and head to /vmfs/volumes/datastore/VM
>>>
# ls -l virt_switch0-flat.vmdk
-rw-------    1 root     root     2147483648 Nov 14 21:57 virt_switch0-flat.vmdk
<<<

2) Create the new descriptor file using the file size of the .vmdk image containing the data
>>>
# vmkfstools -c 2147483648 -d thin temp.vmdk
<<<

3) As result of this a temp-flat.vmdk file will be created, delete it!
>>>
# rm -r temp-flat.vmdk
<<<

4) Remaning temp.vmdk to the actual descriptor's file name ESXi is nagging about
>>>
# mv temp.vmdk virt_switch0-000001.vmdk
<<<

5) Lastly, edit the newly created descriptor file and rename the following 
{ RW 4194304 VMFS "temp.vmdk" }

to 

{ RW 4194304 VMFS "virt_switch0-flat.vmdk" }

6) Also remove { ddb.thinProvisioned = "1" } if the virtual disk uses thick

Done.