The man is described as white, aged about 25 to 30, of a slim build, 5ft 10in tall, wearing a black baseball cap, black pullover, and black jogging bottoms.
A police spokesman said: “Officers attended the scene and conducted a thorough search of the area but no suspects were traced.
“Police later received another call to reports of men who had been selling TVs in the in the car park of the Tesco on the same day.
“Upon getting the TV home, the buyer discovered it was faulty.
“We would always advise the public to use reputable retailers when buying electronics.”
•If you have any further information that could assist officers, please call Hertfordshire Constabulary via the non-emergency number 101, quoting ISR 370 of November 10.