I'd offer to help look, but unfortunately I don't think that's possible, due to the reliance on random numbers in the generation of a world. I zoomed in on that section of your jpeg, but couldn't see anything. About the only other possibility I can think of is that the pothole is somewhere in the middle of the river rather than the end, and that each of them is actually 2 different rivers converging on a point, rather than a single river moving to an endpoint. Good luck!