I am mildly confused

[C101971]

This is my first post here so if this has already been asked and I could not find it, apologies in advance. Anyhow, I know my way around vehicles pretty well, and I ran into an issue driving home from work that I literally have no explanation for after taking apart the whole cab of my c10. It's a 71, and in the middle of driving home my horn decided to short on a piece of metal. No big deal right? Well no it's a big deal, if you can imagine driving in rush hour and your horn goes off whenever you push in the clutch is a big deal. After painfully making it home I pulled up and put the e brake on and turned the truck off. Now the horn won't shut off at all. Disconnected the battery to not draw any more attention then I already had. And checked ALL the wiring, not a nick anywhere, pulled out the relay and put in a universal one I had kicking around that I knew worked. Same problem, horn wouldn't shut off. Wired it to an auxiliary switch, same issue, would not shut off. The only way I got the horn to not make me seem like an idiot was to cut the wire going to the horn or disconnect the battery. Just out of curiosity who has experienced this ridiculous problem?