While the rescued crew members of a Soviet freighter spent the day shopping in Washington, Oleg Sokolov, charge d'affaires at the Soviet Embassy, called on Assistant Secretary of State Rozanne Ridgway to give "thanks . . . for the expeditious and effective help rendered as well as for the care and the friendly treatment accorded to the Soviet seamen," an embassy spokesman said. The crew is to leave for Moscow today. Crewmen were plucked from their listing ship 220 miles off Delaware Bay Saturday by Coast Guard helicopters.