I have no problem with yobit in terms of withdrawal, they always give a tx id even though it does not appeared on the blockchain yet which is kinda weird at first but then eventually the transaction appears on the blockchain, I think you need to wait for a while and see if the coins was already sent, if not you can reach out to their support again and wait if they will take action if not then open a scam accusation on this board: https://bitcointalk.org/index.php?board=83.0  and tell the case in detailed manner.