I wouldn't recommend letting it stand in water for more then 15 minutes.* Do you remember if it was rootbound with a very tight rootball and roots that went round and round?* If so, you only potted it last week, I would suggest you take it out of the pot and take a look at the rootball.* I think I gave you pictures of a rootbound plant before.* If not, lmk.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.