Christ is in our midst!!
Your solution may make your prosphora soggy. May I suggest two solutions that I have used with dry bread? One thing that has worked for me is to place the bread into the microwave for a few seconds; it seems to soften bread enough to be edible. The other solution is to put it into a strainer above about half an inch of water and steam it. In both cases, it's best to watch closely so that on the one hand it does not become even more dry and on the other that it gets soggy. IMHO, putting it into a jar with water will mean it will just act like a sponge, making it inedible.