I am thinking it may not have been in a happy location as it shouldn't have decomposed regardless whether it was attached or not. The fact that it detached from the original rock might have been an indicator of that. I always put mine in a half clam shell with bridal veil pulled over it and a small zip tie for the loose ends. Full light on the sand bed. Generally takes about three weeks before I take the veil off. The local craft store has these 4" or 5" round veil pieces for some wedding purpose that work perfect. It has never failed me. Before that, I lost several due to not being attached. Sorry about the loss, but don't give up on them. They are some of my favorite shrooms.