[Sporktacular]

"US would have trivially recorded them."

Depends on the frequency range being continuously monitored. If it's above the usual signals intelligence range there's a good chance it wouldn't have been recorded.

"Yet that didn't happen."

And we wouldn't know if it had. Holding on to what you can detect and attribute carries advantages too.

[sudosysgen]

We're talking about repeated attacks at around 1.4Ghz, so not only within the range of SIGINT, but it would literally fry your phone, and they were supposedly repeated.

As for the last one, if there was proof, then the State Department wouldn't abandon the theory, and such wildly speculative and substance-less research wouldn't be commissioned.