Two more things:

1) Get your insurance company involved ASAP. The VX was stolen, your insurance should cover that, it doesn't matter that you handed the guy the keys, it was stolen through fraud, but stolen nonetheless.

2) If it does show up on ebay, the seller will *not* be happy to hear from you. I suggest talking to a lawyer BEFORE saying anything to the seller. Failing that, it would probably be wisest to send a certified over-night letter to the seller informing him that the vx is stolen, which would prevent him from selling it to anyone else, then you'll just have to figure out how to make him give it back - probably a fight that you would want your insurance company to handle, not yourself personally.