Hi, I assume your Sans is an all green S. trifasciata, or the yellow-edged version, S. trifasciata 'Laurentii'. Your Sans likely received far too much water while you were gone, and is rotting back. Let it dry out completely,
then water sparingly. If it's not completely rotted, it should come back from rhizomes that are still alive, you should see some new growth in a couple of weeks. If this plant has some sentimental value, and if you feel some firm rhizomes in the soil mix, you could take an insurance cutting to try to grow independently of the main plant. Cut a piece as large as possible with a clean knife, and try to get some roots with it. Lay it near a window where the rhizome gets good light but not direct sunlight, this is to let the cut ends of the rhizome dry completely, so more rot doesn't occur. Might take several days to a week, no big deal to these tough plants. Once the ends are dry (they will look light gray or white) plant the rhizome on the top of an well-draining mix, with the roots in the mix. If there are no roots, just lay the rhizome cutting on the top of the mix, and settle it a little way into the mix. Water sparingly til you see new growth from the growing tip, or growth from the 'eyes' (nodes) along the stem if there is no growing tip.

Feel free to post me privately if this isn't clear, or you
have more questions.
Russ
chammer@cfl.rr.com