Serial numbers aren't that easily removed when they are imprinted in the frame, they would have to weld over them and then file the weld smooth, and then repaint. It's likely they won't even bother removing the serial numbers, because there are thousands of bikes out there that look the same. They just won't likely bike past the spot they stole it from. Definitely file a police report and give them the serial number. Also check with your tenant insurance/home owner insurance policy, it may be covered.