The San Francisco Conference in 1951  

The San Francisco Conference was held from September 4 to September 8, 1951 in the United States to discuss signing a Peace Treaty with Japan after World War II. At the Conference, the Soviet Union delegate proposed to hand over the Hoang Sa and Truong Sa archipelagos to China but that proposal was rejected (48/51 votes). 

On September 8, the Treaty of San Francisco was signed, in which Japan renounced all rights and title to the Paracels Islands (Hoang Sa) and Spratly Islands (Truong Sa). There is no mention of the handing over of the two islands to China.