This is one of the song that many experienced investors used to tell people being careful about exchanges. Since you don't have access to the private keys then it can never be your coins. Even with these kind of senerio that had been happening for long now, some people still keep all their coins on exchanges to hold their and most time, they even stake it and expect big APY which can be profitable but still very risky. We should learn from other people's mistake and keep our coin in our wallet to avoid painful story like this.