After a little encouragement from Cyndi, I decided to try to fix the footie rather than frog it. So this evening I dropped those four cable stitches down to the mistake, then reknit them with my crochet hook.
I'm really happy with the result. If you know what I did, you can see the difference in the cable, but I think that once the sock has been washed and blocked a little, it will be unnoticeable.
I've added a little arrow so you can see where I fixed the cable. It's just a little larger than the rest. At this rate, I'll finish this pair tomorrow or Wednesday. I think I'm going to make another pair for a friend, too. Doesn't everyone need a pair of nice warm footies?