If it is just the vmdk files and not the flat-vmdk files you have deleted, the it is possible to recreate them using the step-by-step guide from KB1002511 ( http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1002511 ).
If you deleted the flat file, then you will have to restore from backup.