Even if you were able to get the IP, that is only the start of the task. You then have to find the ISP linked to that IP, then you have to email them to ask who was assigned that IP at a specific time (this has to be quite accurate), with IPs from your ISP (or perversely theirs) they are usually dynamically assigned and over the course of say a day that IP could have been assigned hundreds of times.
This too would likely be where you got told to sod off, because you would also have to get the ISP to give you the users address and ISPs are somewhat reluctant to release this kind of information without say a police request/warrant, etc.
Personally I doubt the police would be very interested, if they are anything like the UK police, bone idle and for a low value item (I know to you it isn't low value) even less.
Recently a man's BMW car was stolen and he found where it was parked, he called the police, they said they were too busy to send anyone, but they said they would send someone to tow it away and for that they would charge him £110. He had wanted them to catch the thief, but effectively that wasn't going to happen and they were going to add insult to injury and charge him £110. So he had someone bring him the spare and he drove it away, no justice.
