It probably experienced shock. You don't say when you brought it in, where you live or how cold the temps were outside at night when you brought it in. If you already had the heat on in the house, that could easily cause the plant to shed it's leaves. The leaves of a plant are expendable and will grow back with the proper conditions.
You may need to either repot it, cut it back or cut it back, root prune and repot. If you need a site with info on repotting let me know. You should find this helpful too.
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.