I'm purely speculating here, but as each node stores a copy of the blockchain, if every single node was destroyed I would think that all data surrounding bitcoins would be destroyed along with it - the same way that if every bank were destroyed (along with every copy of everyones bank statements) we would lose all data surrounding bitcoin. However, in reality this would have an extremely minuscule chance of occurring. I expect copies of the blockchain would be stored on some pretty secure servers, along with non-networked nodes (which may not have the up to date blockchain, but at least may have some data).

If every node which has blockchain information is destroyed at the exact same time, we probably have bigger issues than what happened to the blockchain (namely, what caused it).