Camping's prophecy was actually a 4-part prophecy, spanning 5 months:
1. Rapture of elect on 5/21/11
2. Earthquake huge enough to throw open every grave worldwide & toss the remains out of them, on 5/21/11.
3. Plagues/catastrophes globally, starting on 5/21/11, continuing to 10/21/11, for the unsaved who didn't get raptured.
4. Destruction of the world & its unsaved remaining inhabitants, by fire, on 10/21/11.
1,2, & 3 didn't happen, 4 remains to be proven/disproven.
Yet, Camping is now adding 1,2, & 3 to 4, saying that all will happen on 10/21/11.
Further, he is saying that something happened on 5/21/11: the "undetectable" "spiritual" event of God's no longer saving any more souls as of 5/21/11.
Yet the "something DID happen" that Camping now claims is in fact not a new claim: the fact of salvation being impossible for those left behind after the Rapture was already partof the first (4-part) prophecy.
Thus, Camping has created a tautology (an undisprovable claim/ an unnecessary repetition of a statement using different words, but adding no new information, clarity or force to the original.) We cannot disprove that the "undetectable" has occurred.