Fortunately the same thing had happened to me at my knitting group the night before, and I'd learned how to undo just the cable and knit it back up. Of course, I don't have any dpns (I just learned to knit a month ago after crocheting for years) so I made do with a yarn needle and several cable needles. (This is my first cable project, it's the "Cable Sampler Scarf" from "Knit Along with Debbie Macomber".)