Mystery Plant

[QueueBa11]

The fact that the leaves died away in a week made me originally think it was some sort of cryptocoryne. Then I remembered that hygros also lose their leaves if they are grown emersed and then later submerged.

Until the op comes back, can anyone id my plant with certainty? Or better yet, does anyone else have a plant like the ones described?

 

[QueueBa11]

Did some more searching, and based on pictures that I see, the op's plant looks like an Alternanthera except that all the plants online have red leaves. The red ones seem to be a cultivar but I can't find any wild types.