Did this once. I put it into a starter and ended up with no activity. Tossed it and purchased a new packet.
Mine had been frozen due to a power failure during the winter. I don't know how long it was iced, but it was pretty much ice when I pulled it out. I recommend trying a starter to see if you can recover it or just getting a new pack. Even if there are some active cells in the pack, it will not be sufficient enough nor of quality to pitch without a starter.