I don't know about reversing it from drying out, but it sounds like the container/bottle doesn't have a proper seal ad is the cause of it drying out. I would recommend placing it in a new container (if its not too far gone) if you are unable to find where the air is leaking in.

The only cure is to heat it and stir it just like you would with a substance with crystalized sugar in it. That is if you can stand the stench ;)