It really depends on how much data was lost - i.e. what size were the missing delta files. If they were quite small, it might be possible to recover by editing the snapshot chain. This KB details how to do this: https://kb.vmware.com/kb/1007969
So, for example. If you had a VM that had a couple of layers of snapshots - vm.vmdk is the base disk, vm-000001.vmdk is the first snapshot, vm-000002.vmdk is the top level snapshot where writes currently go.
Let's say vm-000001-delta.vmdk gets deleted somehow. Now the VM will not power on because the snapshot chain is broken. The parent snapshot of vm-000002.vmdk is missing.
Sometimes you can fix this by editing the .vmdk descriptor. So you would edit vm-000002.vmdk (NOT the delta file - just the descriptor file). You edit the PID value, and the 'parent file name hint' value within that file. The PID gets changed to the CID of vm.vmdk. And the 'parent file name hint' gets changed to "vm.vmdk". Basicaly we are telling the VM to ignore the missing file - now vm-000002.vmdk no longer considers vm-000001.vmdk to be its parent. It thinks its parent is vm.vmdk.
Like I said, whether this works depends on how much data is missing. You may find the VM powers on but does not boot properly. But, if you are lucky and not much data is missing, this may work.