Hello Richard,
You have the best 2 people looking at your problem when it comes to recovery.
One additional note to what Ulli and André said, is to check your Windows Defender and make sure it did not just move the disk slice into quarantine.
Because if it is still there then you might be able to restore the disk slice.
Without that.. you'll have to either locate the missing slice from a backup or recreate that slice.
As you have a LOT of snapshots.. a couple of remarks.
1) It looks like you resized your disk over time. There's a bunch of snapshots with 21 slices and some snapshots with 41 slices.
2) You should not keep snapshots open for a long time. At least not on a VM you care about. If you need that kind snapshots then it is better to make backups. Not only is there an increased risk of the VM breaking due to the long snapshot chain, it is also slowing down your VM.
3) In Windows Defender, make sure to exclude all the vmdk files (even better all vmware file types) from on access scanning. If you need to have antivirus checking your VM then install the antivirus product in the guest OS.
Good luck!
--
Wil
