A few years ago I had a laptop stolen by someone I knew. We lived together in a share house and he took my laptop with him when he moved out. He ignored requests to return it.
When reporting it stolen, I gave the police his full name, his mobile phone number and his Dad's full name and mobile number. As far as I know, they made no attempt to follow this up.
So the moral of the story is: don't bother, if you know where the thief is, "send the boys around" instead.