There should be an ID plate with a serial # on it, which you would need to register it so it should be on your registration. If you haven't done so, report it to the police and give them your info. Keep an eye on CL too, my guess is that they stole it to sell it since it's close to the holiday season.
I had one stolen about 4 years ago, except they only got the frame and bed, no axle or wheels on it. I saw where they dragged it down the road but I eventually lost the trail. Reported it to the troopers but it was never recovered. If anyone owns a trailer, engrave the last 4 of your ssn on it somewhere where it can't be seen easily, will help tremendously should the cops get lucky and find it.