Driftwood is bad for getting moldy when it stays wet. But chances are your gecko is fine. I get mold from time to time in my cages if they aren't drying out enough (this mainly happens in the summer when it is humid and I mist too much since I live in a very humid area). It's not a huge deal--just clean it up and let things dry out. I wouldn't worry too much about the bug either--if it's just a single bug it probably just found its way into the cage and liked the wood so it stayed there.