But I set the brake, I really did!
 

So I come out of the Pilot in Austinburg, OH and see that my truck had rolled forward and was sitting there with the front wheels up on a sidewalk. Of course I forgot to set the parking brake, right? Wrong. When I opened the door I could see the brake was set. I climbed in and the idiot light on the dashboard said that the parking brake was set. So how did it roll?

It's done this at least once before.

It's a 2009 International Prostar if that matters.

Did you also set the trailer brakes? I have seen heavy trailers push thru the tractor brakes when parked on a slope.

Weak brakes or springs in the spring brakes are broken.

Either way it needs some work, measure the throw on the brakes with springs. Bang the spring brakes see if they rattle.

could be many things, maybe bad quick release valve, did the air blow out like normal when you pulled the yellow button?

could be heavy trailer pushed if on a slope, broken springs in the brake chambers, or brakes out of adjustment.

does it have spring brakes on one or two axles?

A good habit to take on is to leave you truck in gear after u shut the engine down. But yes, there must be a misadjusted break and or bad brake chambers.

So many good insights I don't know who to quote to get started here.

The trailer is a 48' box van with 10k - 12k in freight. I honestly don't remember if it made the normal sound of air releasing or not. It probably did or I think it would have caught my attention. I had pulled forward from the fuel island so I was probably on a bit of a hill. One unusual thing about yesterday was the amount of wind. I was on I-90 next to Lake Erie and the wind was gusting at about 30 with steady winds at about 25 out of the NE. The truck was facing dead south. Did I get sailboated? lol (Along with a slight hill and probably weak springs or a faulty valve or bad adjustment of course.)

It could have been as has been suggested. Especially the broken springs. That would cause you to roll, especially if there is only one set of maxi's on the drivers, as is so common anymore. The other thing could be that the brakes didn't set because of an ice plug.

How is the air dryer? Has it been cycling right?

I got home from my run and took the truck into Penske today to get it checked out. The mechanic said the brakes were way out of adjustment. When I asked him how that happened and don't PMs cover routine checks for that sort of thing he did a lot of talking without really saying anything if you know what I mean.

So I guess the thing to do is test the brakes by seeing how easy it is to overcome them with the engine from time to time.

or you could measure the brake stroke like you are supposed to on the pre trip

Point well taken. I need to learn to be a better mechanic than my mechanic.