Sorry to hear about your loss
But Did you activate your 2 Factor?
when you invest that money you must have activate your 2 Factor in Bitstam account and even in you Email.

I actually have some Damn Question
How you Deposit money in your Bitstamp Account from India its hard to transmit money (As i know and as i heard some news)
Quite Interesting point is for every small transaction bitstamp send SMS and even Email to verify transaction so how your account activated and how your transaction took place?