found mine at the beach, soaked for a good month with lots of water changes, more to water log the pieces after the fist few. They were pretty well bleached out from sun and salt before I got them. Was able to find a few hollow pieces.
I have only picked up pieces from beaches. The rivers by me rise and fall by a lot a few times per year so every piece seems to be rotting or recently dead with all the bark on. It seems around here at least that beach pieces seem to be bleached, bark stripped off, and dry. I just picked up these pieces during my most recent adventure.
I live by a couple of lakes, I have been meaning to go walk around them to see what I can find. Think I will start on my next day off. The lakes are down about 5 feet hope I can find some nice peices.