Sad story, I hope that your case will be settled as soon as possible.
For my part
May 05-03 - I deposited 12.42 XMR especially for the fork of Monerov on HitBtc.
After the fork I've decided to sell my XMR to get my USDT.
As the USDT withdrawal was closed, I decided to bought NEO to transfer it in my personal wallet.
May 06-06 - I connect on my account HitBtc and I realize that I no have my balance of 36.3 NEO i bought previously. I searched on forum and several people have the same problem than me.
I had a few USDT left, I decided to buy 5 XRP to see if it's really a bug.
I do not see them in my wallet too.
I not notice any withdrawals on the last transactions and any confirmation e-mail, so I tell myself that my account is not hacked despite notifications of actives sessions in other countries like Brazil, Russia, Ukraine that I noticed by mail late... Thats is very suspicious
At this moment I change my password and created a support ticket which number #290613 and #290907
And looking in the trades, I notice several trades have been made. Someone have converted all my NEO to ETH, then bought expensive SAN and DAY coins orders placed by him, and then sold the SAN to a very cheap order that was also placed by him. He repeated this process a hundreds times, then all my digital assets worth were almost gone with any withdrawal.
My email has been not hacked and my password too.
I also confirm, that I always use the link in favorites, so phishing were impossible.
From what I have seen, this security problem has been there for quite a while.
Yet, hitbtc did nothing to prevent this from happening again.