IF YOU NEED YOBIT TELL IT TO YOU, ASK IT TO THEM
I asked them 1hr after the ICO had completed, both via their contact form and via their troll box but have yet to receive any answer. Until they do, I will consider the coins not burned.
Yobit always post in the BCT thread of the coin that was involved in the ICO to state that unsold coins have been burned. So far they have not.