That sucks and shouldn't be allowed to resolve that way. Sorry that it happened to you! I just stayed in a Mexican Hyatt and like you, at checkin was given an incorrect price to sign. No idea why. It was roughly 33% higher than it should have been. There wasn't any USD, it was only quoted in MXN so I definitely noticed. Had they tried a bait and switch like you experienced then maybe there's a chance I wouldn't have seen it.

I showed them my reservation rate in the app (in USD) and they promptly fixed this issue for me. Well actually it took him about 5 minutes to do so. And after it was fixed I actually think the MXN total was a little less than I was expecting. Either that or an extremely favorable exchange rate? Another weird thing that happened is even though I was charged the correct amount at check out, I was awarded points earnings as if I had spent about 20% more than I should have been. Right on the bill. It says my total was X, and my total eligible spend was 1.15X

BTW is your "168" username related to "一路發"