Today, I finally got in touch with the insurance lady, who was awesome and kickass. We did a conference call, where she told the oral surgeon's office that:
1. The check was sent out to Oral Surgeon's Name, Oral Surgeon's PO BOX on January 7th.
2. The check was cashed, presumably by someone who has access to that PO Box, on January 18th. (Check number, my account number, check amount number, etc.) This is serious, find out who did it, all that.
3. Also, I (me) am still getting rude phonecalls threatening collections from their office, and that's not okay.
They did almost all of the talking, and now it sounds like they're going to take some serious action. The insurance lady promised to call me back as soon as it gets straightened out. I'm still shaking a little from dealing with it, but I'm hopeful this will finally end the madness once and for all and I can start healing. :)