I don't think so. Kramer's book shows a picture of a pre-Fair opening test IND train with an "S" designation on the signboard, but there is no mention in the text of any shuttle between World's Fair and Forest Hills. Remember that the IND Queens Blvd line was new then (opened in 1936 as far as Union Turnpike; 1937 to 169th/Hillside), and didn't carry the mobs it carries today. With GG service extended during the Fair's run, there was no need for an additional shuttle. Remember that on the old IND sign curtains, "S" stood for "Special", not "Shuttle".