Many years ago, my first overnight into Abuja, on parking the plane, the fuel truck connected and offered to re fuel our 737. We decided to fill the wings there and then in case we had issues in the morning getting fueled.
Next morning on returning to the plane, the flying spanner noticed the defueling hatch open... we were lucky we had only 'lost' a third of one tank.
After a lot of shouting and frayed tempers we just accepted it. Later in the trip I recanted this to an old Africa hand and he informed me it can and does happen. Well we never fell for that one again.