Sorry that didnt' go well, but kudos to you for trying to help your plant.

"this past spring, and all the leaves started going quite wilty. As I've started learning more about plants, I thought I'd investigate. As it turns out, it was VERY rootbound -- as in the roots had broken through the plastic pot and roots have completely enveloped the plastic. "

I would assume it was getting/staying too dry at this point, with very little soil in the pot to get/be moist. It could have been near death already at this point if wilting a lot.

You didn't remove the old pot before putting your plant into a bigger one? That's a huge no-no, but not chiding you for taking bad advice, it happens and is beyond your control. Not writing a paragraph about it to dwell on it, just to make sure we understand what's going on, and ask you to please not do that anymore.

If roots that were almost always dry, from being outside of the pot, have lately been surrounded by moist soil, that could be a problem. Does that sound applicable? The more lively roots inside the original, smaller pot, are probably those which could most easily branch out into new soil in a bigger pot, but not with the walls of the old pot in the way of that.

If you start snipping brown parts off, a little at a time, and don't get to a point where there's green inside, it's dead. Hope that's not the case!

As sad as it may be, are you able to add a pic of your distressed plant? If needed, you can at least get plenty of sympathy.

This is a plant with a very strong will to live, and even though there are a lot of conditions working against it, especially timing, it might be salvable. I'd like to see a picture, too.

Before you post a picture, please follow Tiffany's instructions for determining whether or not the plant is still viable.

Al