It isn't until Murch, disguised as the grunting muscle man Chicken, threatens Abe with being thrown down an elevator shaft, that Abe gives up the location of the diamond—his safe deposit box, and he also gives up the key to it.
Abe only discloses the location of his diamond, his safe deposit box, and the key to it when Murch, posing as a grunting muscle man named Chicken, threatens him by suggesting he will be thrown down an elevator shaft.