Michelle Wilde bought a piece of sand art during a visit to Jerome, Ariz., earlier this month. Rather than carry it home, she had the shopkeeper ship the $145 frame to her. Instead of arriving at her home in Everett, Wash., the package ended up next to a railroad track in East Los Angeles. The frame was gone. The box remained. It was among thousands of boxes recently found littered along Union Pacific Corp. UNP 1.76% tracks in the middle of Los Angeles.