I would remove it from any moisture and let it dry out for a couple of days before I do anything. It may be saved, but boy, it is in rough shape, I hate to say -
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RULE OF THUMB - Orchid + mushy roots (usually)= no orchid.
The stem will have to produce a new root with little intake of food or water ( due to the lack of other roots), so, once you pot it (after removing the root threads that are no longer active) I would be sure and dust it with cinnamon and maybe even a fungicide, as this little guy will probably have several openings for a pathogen to get in. Make sure your medium is sterile, dampen it and microwave it for about 3 minutes - make it steam good. And then, once repotted MIST your plant, don't water it for several weeks. It has had too much moisture at the roots and it needs to be forced into root production; a humid medium can do this; a wet medium will induce rot. A rooting hormone may be of assistance to you here as mentioned.
Best of luck - keep us updated.
Steve