From what I can find, P0442 means "Evaporative Emission Control System Leak Detected (small leak) ". It could be the canister, it could be many other things. A 'smoke test' would be one way to find out. I'd take it to another independent shop. You can use the 'mechanics files' link at the top of this page, or Yelp, I've used both successfully to find a mechanic.
Edit - one possibility is a loose or worn gas cap. I'd remove, clean, and retighten it, and drive it for several days to see if the light goes out. If that doesn't work, I might go buy one (the Vibe's the same as a Toyota Matrix, so the Toyota dealer would have one if a parts store didn't.
Here's a discussion on a Vibe forum: