After the sinking of the RMS Titanic on its maiden voyage, many people asked how such a tragedy could have been avoided. Over the more than 100 years since that fateful night in 1912, much has been written about the size of the ship’s rudder being too small, the inadequacy of the flood controls, and the insufficiency of the lifeboats. While all of these were certainly factors in the calamity, the incident itself might have been avoided altogether if it hadn’t been for one missing key.

David Blair worked as a merchant seaman for the White Star Line. He was originally slated to be the second officer aboard the Titanic and had participated in the ship’s seaworthiness tests and initial journey to its point port of departure for its maiden voyage.

The Titanic‘s sister ship, the Olympic, was under repair at the time. At the last minute, White Star Line replaced Blair with Olympic‘s Chief Officer, Henry Wilde. The rationale was that Wilde had more experience with a ship of that class. (Read about the amazing coincidence of the woman who was connected with tragedies on all three Olympic class vessels).

The reshuffling of Titanic‘s crew left Blair disappointed. Perhaps that is why, when he departed from Titanic on April 9, 1912, it slipped his mind that he had a key in his pocket that might be useful to the ship’s crew. That key unlocked the Crow’s nest locker. That locker is where the binoculars were kept.

At 11:40 pm on April 14, Titanic‘s lookout, Frederick Fleet, spotted an iceberg and alerted the bridge. A short time later the ship collided with the massive obstacle, setting in motion a series of events that would result in the deaths of approximately 1,500 people within the next three hours.

When questioned by a US Congressional commission, Fleet disclosed that they did not have any binoculars for the voyage. When asked whether binoculars would have allowed them to see the iceberg from farther away, Fleet replied that he would have seen it “a bit sooner…. Well, enough to get out of the way.”

Blair’s key remained in his possession until his death. His daughter then donated it to the International Sailors Society. On September 22, 2007, it was sold to Shen Dongjun, the CEO of jewelry retailer TESIRO’s Chinese division for £90,000, and is currently on display in Nanjing.

Read more fun facts about the Titanic.

Learn how the Hindenburg disaster almost destroyed Marvel Comics.