dont freak out because it doesnt solve the problem. there are certain chemical solutions you can google on the internet. if you dont want to use chemicals than there is a brand called mite off that I hear works pretty well. I would either trash the substrate or heat it up above 165 (this temp kills all bacteria, bugs, fungus, mold) you can also take the driftwood out and use a 10:1 water:bleach ratio. ALWAYS disinfect everything if you take it from outside. you can pose a threat to your frogs with all kinds of nasty bugs and diseases. driftwood is a perfect home for hookworms, termites, and mites.
How to Get Rid of Reptile Mites | eHow.com