How is it possible for the only thought stampeding through my mind to be, "I don't know"? 

This isn't one of those times when someone asks a question and I confidently reply, "I don't know, but I'll find the answer for you." Nor is it really a statement at all.  It seems to be as powerful as the thundering hooves storming through Pamplona, resonating within the confines of my cranium.  Not a question, not and answer.
There were no waving crimson flags, no screaming crowds, no pomp at all, in fact, that got me to this place.  Circumstance, yes.
It's as if all sources of incoming information have ceased to be.  Silence from the outside, incommunicado. 

How do you solve a problem that is inexpressible?