NEVILLE ISLAND, Pa. - A piece of sternwheel and Marietta history was apparently lost this weekend as the showboat Becky Thatcher sank at its mooring on Neville Island in the Ohio River, just north of Pittsburgh, Pa. "It's gone - not salvageable, a total loss. It's the end of the chapter for the Becky," owner Jeff Levin said Sunday. Levin said the 83-year-old sternwheeler sank sometime late Friday night or early Saturday morning, and the top two decks had collapsed onto the boat's main deck. "We don't know what happened - a passing barge could have hit it," Levin said....