In cases like this last block, you cannot because the share that solved the block was either DOA or orphaned - so it didn't make it onto the p2pool share chain, and hence there's no record of the share itself.
That's interesting. I suppose wouldn't be necessary to make it to the P2Pool chain; that'd just slow down the announcement of the found block?
No. P2Pool tracks shares, which is how it determines what each miner will be paid when one of those shares is also the solution of the block. In the case of orphaned shares, you add a share to the chain, but a longer chain has already been accepted by the network. Therefore, your share is not added to the share chain and is orphaned. However, because your share also solved the block of Bitcoin, the new block is created and added to the blockchain. Miners are paid (because the generation transaction information is part of the block), but the share itself is not recognized by p2pool. That's why virtually every single p2pool UI out there doesn't show this block - they all base block finds off of accepted p2pool share chain shares. The exception is windpath's node - he scrapes the blockchain data to get the p2pool blocks regardless of whether the share that solved it is on the p2pool share chain.