I did the only logical thing: I looked up the caller's name in a Google search with the word 'scam'. And sure enough, I got multiple results about this IRS-impersonation scam menacing well-meaning (and good looking) taxpayers all over the country.
If there is one feature about the internet I like best, it is perhaps this one. In any situation where I suspect some kind of trick, scheme, or fraud, I usually manage to know for certain after a quick search on Google. It has helped me during apartment hunts and the job search. Now, I'll add 'sorting out unfounded accusations about my taxpaying record' to the list.
Unlike a lot of the highly touted features of the internet, the ability for people to share their knowledge about these problems of isolation for the sole purpose of ensuring strangers do not fall victim to the same solves a real problem that, until the rise of the internet, did not have any hope of a viable solution.