I think I probably would have asked to speak to the manager/owner. I would have explained that I do not generally carry cash on me when I'm on travel, and that I needed to pay with a credit card.

If the machine was broken and they really had no back-up method, I'd leave one of my cards with the manager/owner, along with the name of the hotel where I was staying. I'd ask him to call me in the next day or two when their machine was up and running again so that I could then stop by and settle my bill.

I don't think I would have wanted to give up the reward points for using my credit card and/or be hit with at least one fee for an ATM withdrawl. Just my opinion, but I think that if the restaurant was unable to accept credit cards at the start of the meal, something should have been said then. At that point you can then decide whether or not it's worth eating there if you have to use an ATM to get some cash.