Did no one in the world notice a Hydrogen bomb going off at Eniwetok in the Marshall Islands? No one at all? How does something like that go unnoticed and why was there a delay in telling the public "Hey we made this thing that blows shit up a while back, forgot to mention."
I'm just a little confused on the entire matter. Mostly the delay.
The press knew about it almost as soon as the first device was detonated. However, it should be emphasized that the Ivy Mike test was not of a deliverable weapon. Alex Wellerstein (2012) has a footnoted discussion of documents related to this event on the Nuclear Secrecy Blog. In short, Truman waited until after the election and (possibly) the construction of the first deliverable weapon to announce, but the press had been speculating for months.
Truman's State of the Union address in 1953 does not even really state what happened. It is very elliptical:
And recently, in the thermonuclear tests at Eniwetok, we have entered another stage in the world-shaking development of atomic energy. From now on, man moves into a new era of destructive power, capable of creating explosions of a new order of magnitude, dwarfing the mushroom clouds of Hiroshima and Nagasaki.
This is similar to the language they used regarding the Greenhouse test of 1951 — a thermonuclear experiment — but goes a bit further. They did not publicly admit to setting off a hydrogen bomb until 1954, when the Castle Bravo accident made it quite clear they were doing megaton-range experiments. Most of the information about the Mike shot was not released until two years later.
There were also concerns that it could influence the election one way or another. Mentioning it in Truman's final address is also probably him partially, even if elliptically, taking credit for it.
The Ivy Mike device was not yet a weapon, was still in the category of "experiment." And Truman's "crash program" directive of 1950 completely muzzled the US Atomic Energy Commission with regards to what it could say about the test. There was an acute fear in 1952-1954 that the Soviets might pull-ahead in this area (and, indeed, the Soviets did brag about testing a usable "hydrogen bomb" in 1953 — it wasn't the same kind of weapon but it did involved thermonuclear reactions). (The fact that a top scientist actually lost an account of how the H-bomb worked while riding a train in early 1953 did not help this anxiety.) After the Castle tests the US felt much more secure about its "lead" and its capabilities — they showed that they could manufacture usable, multi-megaton weapons in quantity.