"... 4,300 negatives taken by Robert Capa, Gerda Taro and David Seymour during the Spanish Civil War, groundbreaking work that was long thought to be lost but resurfaced several years ago in Mexico City."
The fact that the negatives ended up in Mexico shortly after being developed is probably what preserved them. Had they been is some basement in Seattle since the late '30's then there would be no story to tell......