Hi,
As has been suggested by Jocelyn you could try SWUS (or SWUE to create an event) to start the workflow again.
If the workflow has been partially executed then it might be better to find out what subsequent steps are missing and then executing them manually either by executing the methods or through standard master data maintenance transactions.
Just figure out functionally why the workflow was created in the first place.
Kind regards, Rob Dielemans