I don't know why you end up using that exchange while people trying to avoid them, did you fall the high value of that coin in yobit than in any other exchange?

To solve your issue, the only thing you can do is, contact their support, explain all the things happened. And ask them if it's possible for you to recover your funds, but don't expect they will give you the private key of the address to recover your eth, coz obviously they will never do that.

And one thing, don't expect your problem will be solved as early as possible, yobit is known having its worst customer support, they reply mostly week(s), worst months. Only if they made their new year's resolution to improve that.