It's definitely derealization. The best thing for you to do is not to give in to the anxiety. The anxiety will prolong the condition. You are not going crazy, you are not mad. It's a tough battle overcomming derealization, but do not become a nervous wreck because of it. Derealization easily becomes depersonalization and you begin to feel as if you are forgetting who you are, or feel as if you are somebody else... This is just the condition. Derealization is a Defense Mechanism of the brain, normally caused by anxiety. In this case, because your brain was already stressed, the casino set it in to protective mode, so to speak. It is not permanent, you must remember that. If your feeling of Derealization was caused by your head trama directly, it would have shown by now as your brain's inability to apply emotion to your surrounding environment, sights, sounds, ect. I do not think this is the case with you. I think it was simply your brain's attempt at protecting itself. It will pass, make your life as friendly as possible, so you can take down your guard.