So when we click on an item in SharePoint (onprem) the item comes up fine but when going to the 'workflows' link it fails saying that it can't find a column 'Approval3' on the list that the workflow was running on.
The 'workflow link' referred to is in the ribbon:
If you go to 'Manage Workflow Inventory' you'll see a list of all workflows on your site. At the far right there is a delete action. It was from here that the workflow was deleted. Clicking on the workflow link throws an error which is recorded in the ULS logs:
System.ArgumentException: Column 'Approval3' does not exist. It may have been deleted by another user.
Approval3 is not a column that was created by a user. I think it is a workflow status column that gets created when a workflow is either published or is executed for the first time. When the workflow was deleted it apparently removed this column.
Any ideas how to resolve this situation?