If you place the paper towel with the seeds onto some sort of dish or saucer, and then cover the whole set up with plastic wrap it will usually stay wet with no additional water. Usually if the seeds have not spouted at all you will be just fine. If the seeds have sprouted and the white root tip is brown and dried out, there is a good chance that the seed is a goner. Consider using a Jiffy-Pot greenhouse for future attempts, this is a plastic container and peat pellets that hold a perfect amount of moisture for almost any vegetable or flower seeds.