Stolen phone

Good eveninng, This early morning i was in the the train station Amsterdam Central sleeping and waiting to catch the train, when i fell someone was trying to steal my watch Immediatly i push him and he just left, after a few minutes I realize that I didn't have my telephone in my jeans pocket. I tried to find him but of course it was impossible. What can I do to try to find the responsible of this situation.

Thanks and hope to hear for you