I believe it's a root plant. It's been in water and under light for a while and it seems to be intact. I ordered it from this site http://www.aquariumplantsandsupplies.com. I like that they have free shipping.
I've frozen a few plants before by accident. Both root and stem plants. All survived. I think it depends on the duration of freezing and the exact plant. No harm in thawing it out and seeing what happens...
They have flat rate shipping and their prices are lower. So depending on how much you order, you may be better off. Plus they ship with heat packs if it's necessary. You can probably ask if they will. I received mine two weeks ago without heat packs but in a Styrofoam insulated box. Of course, I also only live an hours drive away (but at $8/box it was easier to have them ship it or would have cost the equivalent of $12 in gas roundtrip and two hours).
Although they posted recently on the local Aquarium club that they were leaving the area in spring to start their business up in Alabama. So you may not have much time to order from them.
Also, I would be interested to know if your plant survived.