Strange/Simple Electrical Problem?

[harnalien]

I have an electrical problem that started recently. I went out to my truck last week and noticed the horn button for my steering wheel (Grant) was on the floor along with the spring. I put it back in place, started the truck, and moved it to the front of my house. While driving, I noticed that my radio would not come on. The interior light would not come on either. To top it off, my horn doesn't now. The ash tray light, guage lights, turn signals, and everything else still work. I checked the fuses for the radio, but could not locate the one for the horn as I was in a hurry and possibly overlooked it. Needless to say, I am not the most electrially inclined person. Does anyone know what I can check that would effect these three specific things (horn, radio, interior light) while leaving everything elso ok? Thanks in advance.