Hello.
Thanks for the offer to help. I checked my (actually it's my wife's) reservation online, and it still says June 3 to June 4, as it has always been. I even have a printout and the original confirmation email with the correct dates. As far as I can see, the reservation is still there and the dates are fine. I just don't know what's going on with the hotel's system (their "upcoming stay" email even put in a different confirmation number, one which I cannot find online, must be their own internal number?).
I have emailed HHonors as well as the hotel itself. So far I have not heard back...
Maybe I should fax the hotel???