The user that owned the workbench jobs was removed from our instance. Thus we lost all the workbench jobs. I found a nice way to recover these:
The steps below are the instructions to change the owner of a Workbench Agent to a new owner.
Since the user was deleted you will need an administrator to take ownership of the account before assigning it to another user.
Generating a new API Token and saving it will fix the ownership issues related to the Workbench Agent and all associated DataSets.
If you need to reassign the jobs to another user repeat steps 5 – 8 for the new user.
Your jobs should start running after this is done.