IP tracking is useless, because not only device is no it the one assign IP here (or else it been set manually, which no body do that on mobile device), but as it connect to LAN it being assigned a first free private range IP address, which is one of most un-unique things in networking.
Ferther more even with public IP tracking you won't get beyond information in which city the specific device is, or if you lucky district.... lot of people think you can get exact address just by IP which is complete BS, it's a biggest myth of internet technology ever. only registrant of IP address have assigned contact address to IP adress.... which is not you but your ISP. So how police do that? If you do something bad they go to ISP that IP address belong and ask under law who use it and give your adress... in other words your ISP is one responsible to protect your private data.... and yourself included
It's also funny how you guys care so much about MAC address..... which is practically useless beyond LAN or local ISP network, servers and routers beyond your local network your not aware of your MAC address because it is not used at all in TCP/IP standard. BUT! You can find same MAC address in other WiFi networks logs when that same person login to it, but tracking that out is near impossible as you don't have access to thosel ogs, in other words you can only confirm if that specific person was in that specific WiFi network, not track down based on MAC.
MAC is mainly used for LAN device identification, like in IP assignment process (aka DHCP) or any other LAN services... but nothing beyond that. Also rarely anybody spoofs MAC, as rooting/jailbreaking community minority of phone community, so people who spoofs MAC on mobile device is even bigger minority, so it is still reliable thing and i bet those thiefs are not so smart as you guys think to spoof MAC.
Conclusion: IP tracking alone is hard (Except for police), IP tracking of mobile device is near impossible as it mostly use private IPs and it's mobile, MAC is complitly useless not because it can be spoofed but it simply near impossible to track. So you should search of other hints. You would have more options if you would know IMEI of the device, which is phone GSM modem's MAC