This can happen in restaurants, bars, in the park while you relax. These thieves use sometimes different approaches but most of the time someone will talk with you or show you something and the other person will take your phone, bag, purse, etc. Sometimes they work as a team of 3 or 4 and they make sure your item disappear really fast. So there is no evidence if you notice a couple of seconds after. There is not much to say, I believe that in most cases you can be saved by using common sense. Carry just a few items when you go to the street. The less stuff you have with you the fewer things you need to control. Keep your stuff near you all the time. If you do this you should be ok. If you, for example, want to take a nap in the park use your backpack as a pillow. That way you can enjoy and stay safe.