unsolicited knock on the door by "plumbers" in Bloomingdale

From a Randolph Place NW household:

Just after the storm last night, two or more men knocked on our basement tenant’s door saying they were plumbers and the landlord had sent them to check on storm damage. We had not called a plumber. Our tenant is a single female. She challenged them and they could not name the landlord, and after her big dog barked, they left. God only knows what they had in store. Please, please, please – if you are a woman living alone (or anyone), don’t fall for such tricks and call the police immediately. Unfortunately there are still ne-ever-do-wells about in Bloomingdale.