Yep. It was in "Snape, the Death Stopper."


I've felt for a long time that Snape was faking it. The childish
hostility between James and Snape when they were kids doesn't
add up. He should have grown up and moved on by now.

I'm sure that Snape's carefully cultivated hatred of Harry
is for a purpose. Dumbledore tolerates it because it is a
part of Snape's way of fooling Voldemort. Snape is able to
"shut down those feelings and memories that contradict the lie,"
but that is not enough. Eventually, Voldemort would notice
a blank, stone wall where a person with emotions should be.

Snape needs to fill that blank space with something credible.
I believe that this is what Snape put in the Pensieve during
Occlumency lessons. The one Harry saw was just a cover,
which Snape intended Harry to see.