I heard a similar one of an SP&S autobox found on an inaccesable siding on a branch in Oregon. When the BN formed in 1970 , it took several years for a complete inventory .The car was opened and it was full of brand new 1952 Chevies ! The guess that a crooked crew didn't have the cojones to get the cars out and sell them . Reportedly the BN didn't mind as they sold the "antiques" for 8 times the original price ! Boxcars have disappeared completely from the rails over the decades . Another tale was an entire boxcar disappeared ,with its load of Egyptian antiquities(from King Tut's tomb ,of course!). Most likely cars that disappeared are those that were in multi-car wrecks or floods and mistakes in accounting for these , among thousands of freight cars owned by a large railroad. I think we all love these apocryphal tales ,and even more so when they come true .
Some recent true stories are of a Baldwin tank 2-8-2 that was left in the woods after a forest fire in Northern California .This engine was eventually rescued and restores in the early 1970s .Also the abandoned 20" gauge Porters above Morenci,Arizona were taken out of their remote location in the 1980s . A 2-foot gauge Shay was taken out of the woods of Alabama ,and restored to operation at Magic Mountain in the late 1970s .This engine is for sale ,by the way . A Climax was taken out of the woods on Vancouver Island in the 1970s and restored by a private owner there .