Lindsey, thanks for letting us know what the root ball looked like! I'm guessing that it was waterlogged long enough to drown the roots, but it might have been some soil disease or even root-eating pests.
If you have a compost heap, that's a great place to throw "dead" plants. Many come back to life, as if compost was an Elixir of Life.
Or, if the roots have "gone away", you could re-pot it into some small pot with faster-draining potting mix. Probably have to trim away many leaves and stems so they don;t drink water faster than roots can provide it. It might have come back.
