A "Hot Wallet" is where coins are stored on the marketplace's server, a "Cold Wallet" is where coins are kept offsite and stored either in a paper wallet or a offline version of Bitcoin-QT or Armory etc. It's to protect coins from being stolen if the server was compromised. Regarding telling you if you have been scammed or not, well I couldn't tell you. If the site admins decides to refill the hot wallet then you should be able to withdraw.