Broke off the water drain cap?
The Rabbit's didn't have one of these, and I heard the A3s didn't have one.
I think you can just remove it and bypass it... if you can't find one.
Good time to get rid of that check valve near it, I've seen a few people who had to remove that check valve because of the fuel line restriction it caused.... of course fuel can syphen back to the tank if you have any leaks.