You have quite an active imagination.
You realize that in order to do that, Iran would have to build a functioning device (which will be nearly impossible for them to do under scrutiny), test it (completely impossible to hide), and build a delivery system (which would also require testing that would be impossible to hide).
The idea of a "surprise" nuclear bomb from Iran is
ludicrous.
Why build it when they will have BILLIONS of U.S. dollars to buy one from Pakistan, or N. Korea?....Ever hear of immediate gratification?
North Korea doesn't have a working bomb to sell, and Pakistan has no love for Iran and would never sell them one.
Pakistan is probably going to sell nukes to Saudi Arabia, though.
If I may say BULLSHIT! We have NO WAY of knowing what N.Korea has, just as we have no IDEA what MONEY spent by Iran can buy!
Perhaps this can help you, but I doubt it, although others will understand!
Of course we do. Any time there's a nuclear explosion anywhere in the world, the US knows about it within seconds - how big its yield is, etc etc.
NK has tested 3 bombs, ever. The first test was a clear fizzle, and the second two also likely fizzles, since neither had a yield of more than 4 kilotons.
(For reference, the bomb dropped on Hiroshima was 10 kT, and the biggest bomb ever tested was 75,000 kT)