Found this in Wikipedia... so the thought crossed my mind.

In 1947, a popular vote rejected Sikkim's joining the Indian Union and Prime Minister Jawaharlal Nehru agreed to a special protectorate status for Sikkim. Sikkim was to be a tributary of India, in which India controlled its external affairs, defence, diplomacy and communication. A state council was established in 1955 to allow for constitutional government for the Chogyal. Meanwhile trouble was brewing in the state after the Sikkim National Congress demanded fresh elections and greater representation for the Nepalese. In 1973, riots in front of the palace led to a formal request for protection from India. The chogyal was proving to be extremely unpopular with the people. Sikkim was closed and little was known until American climber Caril Ridley happened into Gangtok and was able to smuggle photos and legal documentation out. When confirmed by China, India’s actions were brought into the spotlight of world awareness, However history had already been written and matters came to a head in 1975, when the Kazi (Prime Minister) appealed to the Indian Parliament for representation and change of Sikkim's status to a state of India. In April, the Indian Army moved in Sikkim, seizing the city of Gangtok, disarming the Palace Guards. Within two days the entire nation was in Indian hands. A referendum was held in which 97.5% of the people voted to join the Indian Union. A few weeks later on May 16, 1975, Sikkim officially became the 22nd state of the Indian Union, and monarchy was abolished.[3][8] In 2000, in a major embarrassment for China, the seventeenth Karmapa Urgyen Trinley Dorje, who had been proclaimed a Lama by China, made a dramatic escape from Tibet to the Rumtek Monastery in Sikkim. Chinese officials were in a quandary on this issue as any protests to India on the issue would mean an explicit endorsement of India's governance of Sikkim, which the Chinese still regarded as an independent state occupied by India. China eventually recognised Sikkim as an Indian state in 2003, which led to a thaw in Sino-Indian relations. In return, India announced its official recognition of Tibet as an integrated part of China. As part of a significant pact between India and China signed by the prime ministers of the two countries, Manmohan Singh and Wen Jiabao, China released an official map clearly showing Sikkim as part of the Republic of India.[9] On July 6, 2006 the Himalayan pass of Nathula was opened to cross-border trade, a further evidence of improving sentiment over the region.[10]