Yes, the Exchange could delete the coins which they list and they can do that without any warnings. So i had 4 or 5 times that kind of problems, i couldn't clear my coins from the exchanges because there were no withdraw option left. Also i have the other cleaning problem wihich is in my ether wallet, i have more than 200 shit coins in my wallet and i can't delete them and i really don't know what to do with them..