Huh, what does that mean? Once any nuclear material is moved out of the tunnel there won't be any measurable radiation in the tunnel. And if any senior officials were really concerned about a nuclear weapon, nobody in the federal government would have "failed" to do anything. The case would obviously be top priority and everybody would be working 24/7 to solve it. If any real senior intelligence officials actually believed that a nuke had been smuggled through that tunnel, we would now be seeing a huge amount of law enforcement activity in southern California, and I don't see any reports of that happening. I give the smuggled nuke scenario less than a 1% probability of being true.
Why would they have to smuggle it through a tunnel? With our border security, it would have been easier to simple walk it across.