Flooded with water - 2001 VW Jetta Wolfsburg

It cannot be more than just a coincidence that on Wednesday I take my car into dealership to have a lot of work done on the car, then 2 days later there is huge rain storm. I get in my car to find a swimming pool on the passenger-side floor (front and back)! I emptied out about a gallon of water!
This has never happened before and I think the dealership screwed something up!

I had the following work done:
- new fuel filter, pollen filter, air filter
- new drivers side door latch
- throttle and fuel injectors cleaned
- new cat convertor
- new battery pads
- brake clean
- hazard switch relay replaced (recall)

Any ideas what could have caused this problem?
I read on another forum that it could be related to drain under the battery, moon roof leak, or pollen filter leak. Is there any way that I could figure out which is the culprit before I call the dealership?
I didn't see any obvious area that the water could have came inside the car, the interior fabrics on the sides and ceiling are dry.
Also, where would the water come into the car if it was any of those problems? Does it drain in from under the carpet somewhere?

Thanks!