I think we know because an atomic bomb prototype would have been far too large and conspicuous for an individual to take to, let alone leave at, a bar :)
There were rumors of the iPhone for a couple of years before it was released.
Even funnier, there were quite accurate rumors based on patents of the “true video iPod” since 2003 - a 3.5 inch all touch screen iPod. The rumor sites correctly predicted the iPod Touch down to the resolution years before it was released. They didn’t know that would also be the form factor of the iPhone.
One company keeping a specific product launch secret is different from three or four independent companies and all of their network engineers all conspiring.