The test itself had numerous signatures from the light, heat, and sound of the explosion itself as well as the radioactive traces being spread in the dust and air.
While someone might not have been looking for a the project specifically, did anyone manage to notice the signs of a atomic bomb detonation?
Hi there -- while there's always more to be said on the subject, you may be interested in this AMA with u/restricteddata, aka Alex Wellerstein, in which he talks about the Trinity tests. He also links in that to this article published in the New Yorker, in which the government's explanation of the test (an exploding ammo dump) gets a brief mention. Since that AMA is older and locked, feel free to post follow-ups here.