Dear ma'am,
Floating plants will in no way endanger your froglet/frog. It's give him more space to hide. You can always find either wild floating plants in ponds and lakes, or see if you can get some at plant shops(Make sure these are safe from chemicals.)
Best bet is that you find these hyacinths or another plant that is really neat for bullfrogs, the name of which I can't recall. They both float, are abundant in the Southern U.S. The latter will grow under flourescent lights.
Otherwise, stick with fack plants for now. As for it not croaking, it IS probably a female. They only make squeaky kinds of sounds, needs a male to get her active, some background noise like crickets and other frogs chirping in the summer, so depending on where you live, open the window on warm days.
To keep your frog well, make sure it has a heater, don't feed too many goldfish; give it a calcium powder and don't provide too hot of a basking light.