Yesman knew a lot of things.
So many things, that he sometimes forgot pieces, like what Benny sounded like, or what General Oliver looked like (not to say he forgot the look of his body dropping from the dam, Yesman had that memory saved and replayed when he was feeling down, for a light chuckle), which is not to say that the pieces are gone, just that he didn’t put the effort into remembering things he couldn’t quite recall.
There were some things he couldn’t forget, though. Things about Corry. Things like why she collected mugs every shot she got. Things like where she put her little dinosaur toys, and how obsessed she was with dinosaurs. Things like… her smile.