Oh, I thought, they're probably just scratching their heads over the fact that I've kept a positive balance for the last four months, or something like that. I wasn't in a hurry to contact them, but when I got home tonight from Matt's impromptu party I figured, well, it's noon in New York, and I'm awake; might as well ring the bank.
Turns out, that wasn't it at all. Four attempts were made to charge something to my debit card in mid-October. All were rejected because the wrong expiration date was given.
20th: $183.69 (twice)
All of these charges were made to Card Call Service. I'd never heard of it, and I agreed with Manuel (the fellow who took my call) that this did seem very suspicious, and that I should cancel the card and get a new one. While I was on hold, waiting for someone who would confirm that my card had been cancelled, I kept trying to think of reasonable, non-fraud explanations for this. None of my bills in Japan are handled through my US account, or my debit card. Only one bill State-side is automatically withdrawn from my account, but again, that's through my actual bank account, not through the debit card.
Then it dawned on me.
I received my new debit card in early October, since the previous one was set to expire in September (add a week or two for the trip to Japan). I waited a few days to activate the new card, since I wasn't in any hurry to do it, then cut up the old card and threw it away.
Within the Shimane JET community, we sometimes talk about whether our neighbors are going through our trash, re-sorting it for us; a few of us know for sure.
I guess I know for sure now, too.