Slughorn’s True Memory

Slughorn possesses the crucial memory of Tom Riddle asking about multiple Horcruxes, but initially gives Dumbledore a visibly doctored version. Harry changes the elicitation strategy and persuades Slughorn to surrender the complete, faithful memory.

The information exists inside the source, yet a direct request returns a strategically altered answer. Recovering the truth requires a different interaction strategy rather than simply asking the same question more forcefully.

This is human persuasion, not a formal eliciting-latent-knowledge protocol. Slughorn also knows that he is withholding information.