Too bad you don't have a mud pond, or do you?
I betcha it would do awesome in a mud pond.
I am tempted to try it.
Found on eBay, right?
And is it truly double, no reproductive parts of the flower?
If that sprout were mine, I'd take it out of the baggie (no nutrition in there) and gently plant it into some good old compost/topsoil mix using my recipe, in a 12" wide hole-less pot.
Plant it just enough to get it stuck in the soil, then I'd gently place a couple small flat rocks around the top of the tuber to keep it in place. I know it's tiny and hard to do, but I did this with the nearly microscopic Nymphaea pygmaea sprouts. Cuz when they floated for too long, they withered away or disappear (something ate them?). Then I'd put it in full sun, about 18" deep, perhaps putting the pot over a reptile heating pad to keep the water uniformly warm. I use the reptile heating pads when starting a lot of seeds, cuz they don't get too hot (found a load of 'em at a yardsale, all for $20).
Here's a link to one online, so you know what I'm talking about.
http://lllreptile.com/store/catalog/reptile-supplies/heat-pads-heat-panels-heat-cable-and-rocks/