Well, I'll give a really lame update--I showed it to the salesperson who sold me the car, and and a dealer service advisor, and they both told me they had no idea what it is. I still haven't pulled up the carpet to investigate further. The dealer did confirm that car did/does have a Lojack system, but it "should have been" deactivated when I bought it. For now I'm assuming it's something to do with that, or some kind of GPS tracker from the loan company. (although my credit is very good, and my loan amount is small relative to the value of the car)
No one has ever had access to the car except for Ford, whoever shipped it, the selling dealer, and me. I bought it as soon as it came on the lot, and I've never had it serviced or out of my possession long enough for anyone to install anything. And it's always been garaged, except when I'm out shopping or parked at work.
Sorry if I gave anyone the blue balls with this. I wish I could close this thread but that doesn't seem to be an option.