Yeah, that's a possibility. But the IRS has been updating their software in recent years. I have seen letters to taxpayers from the IRS that the IRS would not have sent out years ago, but they can now because they are able to correlate more data.
The IRS knows if you have HSA activity because the HSA custodian has to file reports to the IRS about such activity...I guess if it's not done now, it will be soon that the IRS will require reports from insurance companies, too...
