Truck wouldnt turn over

[shrike]

I was driving over the weekend and stopped for lunch after about an hour of freeway driving. When I came out, the truck wouldnt turn over. I could turn the key, but got nothing. No click, no buzz, nothing.
All the electricals worked, and I could start it by jumping the solenoid.
After I got home, I got out the electrical tester and found that there was no juice coming from the ignition wire. I crawled under the dash and found the wire was hot (when the key was turned) at the switch, but not by the time it got to the fusebox.
I pulled the fusebox, looked everything over and put it back together and then the truck would start normally.
I think the switch on the steering column that prevents you from starting the truck in gear was loose or going bad and it got moved enough to re-establish the connection.
I was wondering what this switch is called? I would like to replace it.
thanks!