UPDATE: it was a flex reimbursement. I signed up for direct deposit a few months ago and totally forgot. I knew I had submitted a flex claim, but I submitted over $200 in receipts so that was the amount I was watching for (though I was watching for a check in the mail). The reimbursement was for $194 because that was all the money I had left in the account.
But I am surprised the bank couldn't say, "this came from TASC (our flex spending program provider)".