[greasemonkey]

Code readers can be had on the cheap, I think I used a discount and got one at Advance for $50 or so. Handy little thing. It reads and clears codes. I find it hard to believe that a shop with the ability to fix a car would not have a basic code reader. How would they even know if it was fixed and the code wasn't still active?
Assuming the problem has actually been fixed, you can pull the negative battery cable to clear the code too. I used to do this after getting a code read and fixed but didn't have a scanner. Stores here won't let you clear it with their scanner, maybe you would have better luck.