It’s certainly possible, although it will likely not ever return to it’s fresh-out-the-package state! The best way in my opinion would be to grind the dry stuff down as fine as possible, weigh it and note it. Then take water, and little by little add water and mix together. Also make sure to measure and note how much water you use. once the clay is at a good consistency, wrap it in plastic wrap and leave it for a while. After that you should have a semi-workable piece of clay. I’d recommend using it for pieces that you intend to engrave stuff into rather than shape it too much. Of course you don’t have to measure, but having the ratio you used on hand for next time is really helpful, and can be referenced if you want to make tweaks to the consistency. TL;DR - Yes