Lotus have evolved to be photoperiod sensitive and that means once the days get shorter, energy is funneled from photosynthesis to tuber formation. The cellular metabolism slows and the cytoplasm is chemically altered in such a way that it functions as an 'antifreeze' of shorts. Because of all the changes....the leaves die off and the tuber is a starch storage organ, that will feed the sprout next spring until photosynthesis is re-established. The plant is now prepared to withstand wintery conditions.
I'd feel gently sound the potted plant and see if you can detect a tuber....which hopefully I am right and it is there < g >....if you do, I would leave the plant in the pot, undisturbed, and leave it in a cold place, like maybe the bottom of the pond? If you keep the tuber warm indoors, the danger is that it may try to grow and, without the ability to photosynthesize, the tuber will be expended and once the plant will essentially starve.....lacking the nutrient stores to support the plant growth in the coming growing season.
Truth is not what you want it to be; it is what it is. And you must bend to its power or live a lie.”― Miyamoto Musashi
"Knowledge speaks, but wisdom listens." ~ Jimi Hendrix
“The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.”― Stephen Hawking
Craig