Amused to find this. I am trading on Bittrex for 4 years and so far so good. Are you verified customer? Did you contact support? I know they are very strict to some immorality of users ( like taking part in pumping groups) but I never expected they would empty user's account. I would advice you to go to their slack group and raise up the issue there. It may help.
I'm not an immoral user for example, i didn't take part in a pumping group or other strange things, but bittrex was very very unfair with me.
My withdrawals are still locked at 0 btc daily limit, but my deposits are still full functional... so i can deposit there as much as i want loosing then my funds. Is that fair!?
bittrex should be ashamed about their behavior.