I'm sorry for the long delay,
@dmertz and
@TurboTaxBillMc. I finally had time to call the HSA administrator tonight. They told me that because I made the contribution during 2017 for 2016, the contribution would show up on the 5498-SA's for both 2016 and 2017 - and oddly enough, I can still make more contributions for 2017 until April 15, 2018. I didn't receive a 5498-SA for TY 2016 during 2017 because my account wasn't active until after January 31, 2017. They're going to send me the 5498-SA for TY 2016, and I don't have to amend my return.
