In what circumstances would an AC produce no condensate but still cool the air

Sometimes it is necessary to adjust the fins on the downstairs vents to restrict some of the airflow so that more will make it to the upper level. This is especially true in cases where there are no dampers in the ducts of the type described by BMitch in his answer.

I have a similar problem in my own two level house where I have to adjust the vent fins two times per year to set the proper upper / lower level air flow.

Another important question for you.

Have you checked the primary furnace air filter to make sure it is clean? If this has never been changed it could be restricting the air flow design of the whole heating/cooling system. I've seen these filters so clogged up with dirt and dust that it was a wonder that the furnace fan was able to circulate any air at all!!

Don't forget that the percentage humidity is RELATIVE. Cold air cannot contain as much moisture as warm air. For the same amount of water in the air, the relative humidity will increase as the temperature drops. By consulting a psychrometric (humidity) chart, I see your overnight run removed 19 grains of water per pound of dry air. If you rewarmed the morning air back to 81 deg F, the relative humidity would be about 52%. Or, if you cooled the initial air to 72 deg F without removing any moisture, you would get a relative humidity of around 88%. So despite the higher relative humidity reading, moisture was removed.

The moisture removed is a function of the temperature of the evaporator coils in the A/C unit and the volume of air flowing through it. As bib pointed out, the unit may not have been actually running that much, reducing the volume of air passing through the coil, and thus minimizing the dehumidification effect.

If you continue to cool the same air and avoid introducing additional moisture, the humidity level will eventually be reduced. It will take some patience.