I'm missing a screw for my neck pickup!

These have become lose before, but never completely fallen out. And now that I can't find it, I'm not sure what to do. I mean, I never really use the neck pickup that much (I really like the sound of the one in the bridge better), but I'm still concerned. Any advice?
I had the same problem with a screw in the jack of my guitar. Just find a screw the same or near the same size and fit it in there.