Chrysler uses the absolute worst (cheapest) hose clamps I've ever seen. Trace the evap system and look closely at hose clamps and all hose ends for signs of failed clamps and/or cracked and split hoses. Good clamps are cheap enough at under a buck a piece and hose can be bought for under a dollar a foot. I'd start my search around the canister.

In your case, since you've already been to the dealer, I would bring it back and tell them they didn't fix the problem. But in the future, unless it's warranty work, I'd just hunt down the problem myself and probably have a handful of good clamps and go ahead and replace any I come across...