Get someone to stand outside your car with a hose, while you were inside. It's helped me find leaks on friends cars.
Also if your carpet has been getting wet for a while, pull it back and let it dry out or you will get mold/rust issues under the carpet.
You might even find you have to replace the carpet if it's been a while.
Basically, pull it back though and get a carpet shampoo'r and do both sides of the carpet, and let it dry out before you put it back.