Advice Needed

[Kunis]

I booked an escort last night but left as not the same as her pictures and she got upset somewhat when i said i was not staying.
So I opened the door and made my way downstairs and out the main door, I checked a text and then started walking and was hit from behind and someone shouting B*stard, and fell to the ground, was dazed or out for several minutes and when I gathered myself and got up, i checked my pocket and thankfully the 100 euro, the fee was still there but smartphone screen was cracked but worst of all my gold ring was missing.
I tried to contact escort as wanted to see what she would say but no answer and door shut.
Its a nice apartment area but didn't see any cctv there either so what can I do.
Has it ever happened to other guys?