The second divine key was hidden and located in some space time pocket. This dimesion pocket make sure that its contents isolated from any detection measures. That's why Schicksal could not find the key for a long time.

The key has stayed for eons and never been moved from its place in London and it was always under protection of The World Serpent, Jackal and Raven.

Knowing all the hints, Otto Apocalypse dispatched specialist mechs with advance EM scanner to locate the keys by rounding the area. The mechs will send signals and mech on the opposing side will then receive the signal.

If dimension pocket is in the middle, it will interfering the signal and make the signal received faster on the opposing end. After they located the divine key, the key was covered by distorted geometry 50 meters above Thames river.

When honkai beam launched to the divine key's cover, it started to revealing the divine key itself and it was huge like a massive locomotive.