We were trading in dollars with Pakistan. They still owe something to the tune of $500,000 for medical items they bought from us. I don't think INR was used to trade with Pakistan. Even if they did use INR will stay in Indian banks assuming one of their banks have accounts in their name. And I am for all trade being suspended as well. If that does makes them bleed then better off if there is no trade.You may not trade fake INR for USD, but can certain buy a lot of India stuff with fake INR, thereby preserving dollars, so essentially the same effect. This goes with the fact that there was robust trade between India and Pakistan, that not only gave them required items cheaply but also preserved their dollars.
Now there is no trade and they are forced to buy everything with dollars. So stopping trade has equally contributed to lack of fake INR. I don't know how much though, but it is important that the trade remains suspended for now.
There are $2-$3 billion worth of imports stuck in their ports and letters of credit pending. If IMF deal goes through then it will unlock couple of billion dollars from other sources. But however, all these will be vanished within a fortnight as they have $6 billion to repay in the form of the external debt payments in the next couple of months.