I also wonder how they expected 18 mL of water to last more than a few days anyway. Perhaps someone smarter than me can answer that.
In any enclosed system the water circulates through the plant, evaporates into the air, possibly condenses on surfaces, then is drawn back into the plants again. There is no need to add water as long as there is enough tongo through the cycle.
This was basically a heated terrarium that did not stay warm enough.