Ok, I figured that might happen. Can you make a make-shift incubator until you can go out and get a real one? A box with a heat lamp (or even a regular lamp for now) over it perhaps? The eggs need to be kept at a temp right around 100 F, so you'll also need a thermometer to monitor the temperature. You don't want them to get too hot or too cold. I'm sure you can find some posts on here about home-made incubators that others have made, I've personally never made one myself so I don't have much more advise other than that. They'll also need humidity, so a bowl of water in the box with them might help for now. Really, they need a real incubator that is enclosed and can maintain a constant temp/humidity for these eggs to finish out their incubation and hatch out successfully for you.
Or if you have another duck/chicken that is broody, you can stick them under that bird instead. This would be the best case scenario, but it sounds like you just had this one duck that is sitting on eggs, right?