I'd definitely make sure the sunroof drains aren't blocked up. If it's been in the foot wells before there's a good chance it's still damp even if you can't really feel it.
Best solution is getting hold a dehumidifier and leaving it in the car for a couple of days and see if the damp comes back.
Just bear in mind that Micras aren't the most well insulated things ever made so they will mist up a lot more than most modern cars.
