Did he also tell you to keep a piece of mylar (from a balloon or vanilla wafer bag) or a piece of tire in your tool bag? You can put one of these inside the slashed tire to keep the tube from herniating and limp your way to the shop.

I used the mylar trick ($ bills also work) when I got a 3/8 inch cut in my brand new rear tire at the Cinderella last year. I made it the 2 miles to the rest stop where I was greeted with the lovely sight of a bike shop van with tires for sale. The shop owner told me about the tire trick.

Cut a short length of tire, trim the bead off and smooth the edges so it can be used as a boot inside the tire. The owner says you can actually ride quite a long distance with this repair.