Your container, is that compost bin that rolls? It has bunch of holes here and there, and if you kept it outside, there is high chance fungal mycelium got into it. Even if you keep it indoor, it is impossible to keep fungi out, but if you placed it outside, then... yea.. it can be preyed pretty easily. I keep all my substrate in progress in my garage, with filters on container. Small amount is okay, as microorganisms can dominate them over.Dang, it seemed like it was doing so well. How do you think this could have happened? It was very delicate and spongey...ish. It smells very earthy like good potting soil.