Honest PIOs? Is letter-writer Manilal Savla sure? Indian currency always had some restrictions regarding convertibility. For a number of years, India's Reserve Bank had restricted non-citizens from carrying Indian currency abroad.
At the airports we can always see notices warning non-citizens from taking Indian currency abroad. There were exchange counters at the airports for facilitating the exchange of Rupees to the foreign currency of the foreign citizen. You cannot blame the Indian government or the prime minister if you smuggled Indian currency into the U.S., violating the Indian custom laws.
Here in the U.S. we hardly keep cash currency. Most of the currency is kept as deposits in a bank. Similarly, if you had kept the Indian currency as a deposit in a local bank, you would not have faced the current crisis which is of your own making. So please don't blame the Indian government, which is trying to eradicate corruption from all walks of life.