Um, especially with 120,000ish.
The average expected service life of a clutch is 100,000 miles. Less if you do a lot of city driving, a bit more if you are on the highway all the time. If you've worn it down to the point where you can let the pedal out in gear and get no engagement I'd wager you've put rivets into the flywheel (but I'm not sure how you could have missed the horrible noise that should have made) and destroyed the flywheel.
The other possibility is that your trans is FUBAR, but since it happens in all gears the clutch is a more likely culprit.
You sure no one stole your drive shaft?
Also, when you let the clutch out, does the pitch of the sound the truck makes change? It should change slightly as the weight of the things in the trans start dragging on the engine.