sit in the car and have someone gently rock the car.
You may hear water.
Also, go into the cubby holes behind the seats and remove the side panels.
Feel around behind here for water.
If the drain holes block up the water is held in here.
It may be just as easy to remove the plastic side vents and check the drain holes are blocked anyway(should be a routine item) There is a full guide somewhere.
I would have thought that if there is a damp problem enough to cause mould you would smell it.
See if you can find a way to remove the mould and then use a sanitiser spray
(motorcycle accessory shops sell this)
