British Transport Police (BTP) have released CCTV images of a man and woman they want to speak to in connection with the theft at Upminster.
Officers are hunting thieves who cut through a lock and stole a bike outside a train station.
The bike was stolen at 2.50pm on November 5 after the 33-year-old victim had secured it in the cycle shed at 7.30am.
Anyone with information should call BTP on 0800 40 50 40 or text 61016 or Crimestoppers, anonymously, on 0800 555 111.
In all calls, please quote incident reference B13/ESUB of 01/12/14.