A few things you might consider then....
If your email was compromised, rather than monitoring your account 24/7, the clever thing for them to do would be set up a filter to auto delete/redirect incoming mails from Bitstamp (since you have to contact Bitstamp support to actually change your contact details - I don't know what security checks they do though). Check to see if there is a new filter in your email account (they could easily have deleted it after but worth checking). Did they empty your email trash bin?
Also, did you have 2 factor authentication enabled (i.e. via a code on your phone) on your Bitstamp account? If you did (but it sounds like you didn't), then that narrows it down a bit since having your username/password shouldn't be enough for hackers to scam you.
Did you change your password after first logging in to Bitstamp? Under the scam I outlined in my post, if you changed your password and didn't login through the fake portal again (Bitistamp.net), they would (I think) no longer have access.
These things might help you figure out whether the problem is internal or external to Bitstamp i.e. hackers or Bitstamp themselves. I have never withdrawn funds from Bitstamp so I don't know the details of the process, nor am I an IT/Bitcoin expert so I can't advise there. However, if your BTCs are now at another BTC address, you can follow your coins in the blockchain or obtain the address from Bitstamp, then you may consider contacting a Bitcoin forensic expert company such as mentioned in this article http://www.bitcoinbulletin.com/2013/08/14/btc-security-evolves-now-you-can-recover-stolen-bitcoin/ (UK based - I have no experience with them, I just stumbled across the article).
Regardless - sorry for your loss. It does sound like a bad dream.