Etydhv

It's August 6th, 1945. The first atomic bomb ever dropped hurtles to the ground. Its fuse fails and with a thunk it buries itself in the ground. The Enola Gay flies home, it's crew worried they did something wrong.

Now the brass back in Washington have a problem; they just hand delivered an atomic bomb to their desperate enemies, and it might be easy to repair.

I couldn't find any contingencies about it, but I'm also not a professionally trained historian with access to primary sources. I did find plans, which were abandoned, for building a giant concrete containment vessel around the Trinity device in case that failed to completely detonate, so they could save the uranium.

My question is, what, if anything was their plan for this situation?

...win the war anyway within a few months, and pick up the wrecked bomb from wherever the Japanese had stored it.

Even if Japan could figure out what that bomb was supposed to be doing and repair it, they didn't have any delivery system that could reach mainland USA (with any degree of certainty).

More importantly, the USA knew Japan did not have the capacities to build a second bomb, so even the microscopic chance that Japan could deliver the salvaged bomb to some target would not have changed the outcome.

The USA had both the delivery system and the production capacity to build a second, third, fourth bomb, quite aside from having the strategic upper hand so firmly that they did not actually need the A-bomb to win the war. Not even in the very, very unlikely scenario of a major city, Pearl Harbor, or any other single location taken out by the salvaged Little Boy.

The primary contingency plan was the design of the bomb itself. Little Boy was not a safe design: any number of unplanned events could cause a detonation. Foremost among these is impact: a 500 g impact, such as would happen after a 15,000-foot fall, is sufficient to bring the bullet and target together, detonating the bomb. If the bomb hit water instead of land, the water would act as a neutron moderator, causing a criticality event and severe radioactive contamination. In the event of an airplane crash, any resulting fire will trigger the explosives, setting off the bomb.

In short, once the bomb is fully assembled, it's very hard to keep it from going off. In the event that the crew of Enola Gay had to abort their mission, they had no intention of trying to land with the bomb still aboard.