Depends. You know, it's such a habit for me to pack lunch when I wake up that I cannot imagine forgetting it. However, sometimes I pack too much and leave the rest in the fridge.
I would prob never do the 10 mile lunch commute. I hate driving, and that's my commute. My kids are in camp this summer, and rather than do the mid-day 10 mile each way to pick up, I work from home in the am.
Because I very rarely eat out at all, I would possibly go out for lunch and treat myself, depending on my schedule. My work days are packed, though.
So most likely, I would go to the grocery store. Forget the salad or hot bar, or buying a fresh sandwich from the deli. I would buy actual food that I could eat at home and eat that. I can't eat wheat, so ramen, frozen burritos, and pre-made sandwiches are out. I'd probably buy some fruit, maybe some cheese or meat or yogurt, and a vegetable of some sort.