Recover accidentally deleted storage VMDK (after deleting VM with storage attached)
I had ESXi 6.5 running (part of vSphere Essentials, not vCenter) and my main host OS SSD was going bad. I had this SSD for the OS and app VMs, but a separate datastore (called app_storage) for all the app data (a spinner RAID of about 20TB total saize) on a Dell PowerEdge T430. I had all the app VMs backed up to the RAID in a separate backup folder. I installed a new SSD for the host OS (decided to upgrade to ESXi 6.7) and installed ESXi successfully.
After this, I went to register a VM to get started restoring the application VMs. I made a copy of the backed up folder of one target app (with the VMDK, VMX, etc files) on the spinner RAID (app_storage). I read an article that showed how to register the VM from a backup. I registered the VM, but got an error that the data storage virtual disk (the one that lived on app_storage) was missing. So I deleted the VM thinking I'd start over. Then I realized that about 4TB of data was gone; the entire data storage folder that was for that app. After reading through, I should have de-registered the VM instead. But because the error said that the data VMDK was not found in the first place, I didn't realize it actually attached to the app VM.
Can I recover this somehow? This is very bad for me, as this VM is a critical piece of infrastructure. I've got application config and the PostgreSQL database backed up, but all the artifacts that made up the approximately 4TB of data are gone (a lot of artifact history). This is not the end of the world but will majorly impact this service for my business.
I understand that this RAID should've been backed up, but we are small business and having an entirely separate server of this cost to backup 20TB of data was not yet approved. I definitely learned my lesson, but I really need to get this data back if at all possible.