I believe ChileWilli because the same story happened to me this afternoon!!!
I had 0.15 BTC and arround 52k of safex coins… And left my computer for about 3h, tried to access BitTrex from my phone few hours later and found out that my email was breached in the meantime together with my bittrex account.
I blocked the account, wrote to their support but no answer yet (this happened 2h ago). However when I got home my mac was still logged in there and I could see that my balance was 0. Although I changed password few times in the meantime, and also email blah blah… Very poor security level
I saw transaction history and have IP address (220.127.116.11) that leads to VPS company called Servebyte.
Funny thing is that today morning I registered and created my bittrax account to start tradding so I lasted for 5-6 hours totally with a loss of somewhere about $1200 USD