Exchange is not a wallet. its a simple exchange and always there is a risk of hacking and bankrupt.
Wallet is the right place to store your coins. Do you ever left your money in a exchange office in real world?
Totally agree! If nobody steal it, then you just can loose it, because the exchange not listed coin any more.
Generally speaking, it doesn't happen that way.
If an exchange decide to remove some coin from its trading list, it will give you enough time to withdraw your coins.