yep, same here. i'm 90% sure i've had one of those a while back. it died rather quickly when the rest of the tank was going bonkers with really fast growth. it's most likley a house plant. aquatic lillies have no strength to the stems, uproot them and take out of the water and the leaf will hang like a wet tissue. i'd guess if you pull that out it'll stand erect. if this is the case it's 100% a house plant.