Well, I wouldn't worry to much about that small a leak.
If you can't locate a moist area on the underside of car you can put some newspaper or cardboard under the car the next time you park it and before you move it note where the spot of fluid appears and thus get a exact location for the leak, (right above the moist spot).
It can also be your friendly neighbor walking his dog to do it's duties under the protection of your car
