Looks like a pond snail to me. If I were you, I would scrub your drift wood, unless you boiled it already, to remove possible eggs. Their eggs look like a white jelly and are easy to remove. If it is just the one snail you can keep it if you want as it can't reproduce, but if there is more than one, you might get an infestation.
Are pond snails beneficial in anyway or just a pain?