There are several species of "Frogbit." Was there the scientific name on the package or invoice or list you ordered from?
The "tropical" Amazon species is Limnobium laevigatum. It will grow emersed as a bog plant.
A second species in this genus is Limnobium spongia. It does bear a striking resemblance to the plant you have. I've got an issue with my PC just now and can't load photos, but a Google search of this species will bring up plenty.
There is also Hydrocharis morsus-ranae but I had this one and it looks near identical to the L. laevigatum. Your plant does not look like either of these.
