You might want to check behind the rear quarter trim on your passenger side in case you have a washer leak from a union in that area. My carpets feel bone dry too but I still managed to pull a 1/2 litre from the dehumidifier last night...
DubSteve
I checked there as well but couldnt find anything, the only place I can think it is coming from is down the top of the wheel arch but I dont now how the water would get there in the first place and its impossible to get in there to check it out properly