A while back a similar thing happened to some friends of mine and I know the devastation and police reaction. One set of drums popped up quickly at the local store and we quickly recognized the blood stains on the toms. We didn't get any sympathy from that store or the police. It made us wonder about the equipment that we bought from that store and how many times they get to sell the same instruments over and over.
And the wound still sits very deep. Twenty five years later, the bass player still closely inspects every single cherry Rickenbacker 4001 he sees for certain chips in the paint work. You can feel the electrical charge in the air as soon as he sees one and you really don't want to be around if he ever finds anyone using that particular bass.
To give you an idea of the insurance costs: I have about $14k of cover for about $120 a year. I am in Germany with worldwide cover set up by a nice real lady (not some speaking machine) at a specialist musical insurance insurance company in USA. I am not sure if I can specifically state their name here, but they and their President have been exceptionally good to me. I can recommend them if anyone needs to shop around - but I have not had to test their cover for anything stolen yet.
Good luck and I hope that you locate that 12 string.
By the way, I scratch my name, details, date and serial number on the reverse side of the scratch plates.