They have closed the site but have started emailing customers private keys for the coins they have stored on the exchange. I can confirm I have been emailed private keys for some of the coins I had stored there.

They are gradually working through all the coins they had on the exchange, so the process will take some time. They explain everything in this tweet, and there is also a link to a document with a detailed explanation in that tweet.

https://twitter.com/swisscex/status/576564773892014080

Once you have been emailed a private key for a coin you had o their exchange you have to download and install its wallet. After you have synced it you can import the private key they emailed you into the wallet. After that your coins should show up in your wallet.

ps

Thanks for returning our coins Swisscex, I incorrectly thought we had all lost them.