As per what idle-jam said, If you find that you have only a VMDK-flat and a vswp file and if the is still running perfectly fine (although it is unmanageable from vCentre) then this is the correct method to use. VMware KB: Recreating a missing virtual machine disk (VMDK) descriptor file
I have personally had to use the above method twice and it works perfectly.
The cause of the issue for me was someone performing renames of a VM but at the datastore layer!!
After recreating the VMDK and VMX, a storage vmotion fixed that up and a beating was administered to the user who made the changes.