Campingdad is onto the same thing that I do in similar situations. The only difference is that I use toothpicks. What you need is a small container of toothpicks, you can use round of flat, but I typically use round. Get a couple of them together and compare them to the hole until you have an amount that when held tightly together they will fit "very" snuggly in the hole. Take that bundle and put some wood glue on it to hold it together and pack it in the hole. Use a hammer to lightly tap it in snuggly. Let it dry completely, like a day or two. Take a heavy cutter knife and cut the sticks off even with the current wall, and replace the screw into the new fashioned filler you made out of the toothpicks.
I use toothpicks over match sticks because the toothpicks are typically not as brittle.
Probably be easier to wait til you get home to try and fix it, but if you got the supplies handy go at it. I used this trick on almost all the windows in my father's old camper and everyone of them held, you just have to be patient and let the glue set up.
One other thing, Campingdad did mention that the empty space between inside wall and outside wall may cause a problem. This could be true, and allow the screw to push out the toothpicks, this is why they must fit tightly. If they do not work, do not worry. You are a camper, you are bound to have some kabob sticks lying around. These bad boys are about a foot long and bigger. Take some and put them together until you have a bundle that will fit very snuggly in that hole. Put wood glue on them just like the toothpicks, especially the end that will be inside the wall. Insert them into the hole and push them in until you feel them hit the outside wall. You can lightly tap these as well to secure them in, but not too hard as to damage the outside wall. let them sit and dry and cut them off just like the toothpicks. This way they cannot push out because the outside wall will keep them from advancing any further.
