It did not leave illegal (perhaps some part of it) for the most, the money circulated and was used to pay for the imports (goods machinery etc.), remitting money out of pakistan (corporations, individuals). The important part is that the money could have had better uses, instead we gave up dollars to buy rupees and restrict it supply keeping it artificially high. Now we have none.no its not in Pakistan, it left thru illegal channels and that is the big problem. If it is in Pakistan it must be in some Bank accounts and accounted for then its not a problem.