I had this same issue on a 2005 4 motion I bought used in 2013 (issue only affected the 4motion I believe).
Here is the link http://www.passatworld.com/forums/b5-garage/359378-fuel-leak-venting-issue-2.html
The 2 things you'll run into are:
1) they say the recall was "completed" - question them on what "completed" means. Was it just inspected or was the tank actually replaced. Because of the labor involved, VW isn't going to tie up a tech to inspect the tank just to put it back on, I firmly believe 100% of the time, if it wasn't leaking at the time of recall, they called that "complete". Unless the tank was replaced, the recall was not "completed".
2) there is no statue of limitations on recalls
If all else fails, tell them your kids (if you have them) are sitting on 100 lbs of explosives every time you drive the car, usually gets their attention.
They'll replace it, you just might have to go Erin Brokovich on them.
The problem is a vent on top of the tank that fails. Next time you fill up, pull up the back seat, on both sides are access points. Three phillips screws hold on the plates. Take the driver side access port off and fill up the tank, if you see gas coming out on top of the tank, its the venting issue which is the recall.
I found mine 1000 miles from home on vacation, kept the tank 1/2 full until I got home. VW fixed it eventually, only took a week or two, for some reason the tank has to come from Germany.