I don't know if the OP intentionally misled the hotel or not. And of course, I wasn't there to hear or see the "embarrassment" that allegedly occurred. We're only hearing one side of this, and it's quite possible that the OP was just as rude as he claims the manager was to him. (The statement about walking away and saying "whatever", after arguing for 5 minutes, doesn't exactly paint a perfect picture of the OP)

All that being said, if everyone at that hotel got the night for free, then he should too. It doesn't matter if the price was supposed to be $29, or even if the OP intentionally misled the hotel and the price should be $89, it should still be free, since probably everyone else at the hotel was initially charged the non-discounted price.

As for future free nights - no way. Refund the night in question, and both parties need to move on.